EPA-650/3-74-011
AUGUST 1974
Ecological Research Series
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EPA-650/3-74-011
CHEMICAL CHARACTERIZATION
OF MODEL AEROSOLS
by
Warren Schwartz
Battelle Memorial Institute
505 King Avenue
Columbus, Ohio 43201
Grant No. 801174
ROAP No. 21AKB-08
Program Element No . 1AA008
EPA Project Officer: Ronald Patterson
Chemistry and Physics Laboratory
National Environmental Research Center
Research Triangle Park, North Carolina 27711
Prepared for
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D .C. 20460
August 1974
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This report has been reviewed by the Environmental Protection Agency
and approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the Agency,
nor does mention of trade names ur commercial products constitute
endorsement or recommendation for use.
IX
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ABSTRACT
Model aerosols were generated from individual hydrocarbon precursors
and nitrogen oxides under simulated atmospheric conditions in a
17.3 m environmental chamber. Hydrocarbon precursors employed
were toluene, alpha-pinene, and cyclohexene. Aerosols were collected
on glass-fiber filters and organic matter was obtained by solvent
extraction. Organic reaction products were fractionated into acid,
neutral, and basic components, and were analyzed in detail by tech-
niques including gas chromatography and gas chromatography combined
with mass spectrometry. The study also included evaluation of
techniques for selective derivatization of aerosol products.
A variety of polyfunctional reaction products were identified, in-
cluding alcohols, aldehydes, ketones, carboxylic acids, and phenols,
Tentative identification of nitrogen containing products was also
accomplished, including nitrate esters and aromatic nitro compounds.
This report was submitted in fulfillment of Grant Number R-801174
by the Columbus Laboratories of Battelle Memorial Institute under
the sponsorship of the Environmental Protection Agency. Work was
completed as of April 30, 1974.
ill
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CONTENTS
ABSTRACT .......................
LIST OF FIGURES ................... vi
LIST OF TABLES .................... xi
SECTIONS
I SUMMARY AND CONCLUSIONS ............. 1
II BACKGROUND AND INTRODUCTION ........... 5
III RATIONALE AND METHODS OF PROCEDURE ........ 7
Selection of Hydrocarbon Precursors ....... 8
Generation of Model Aerosols .......... 9
Smog-Chamber Characteristics ........ 10
Smog-Chamber Cleanup ............ 11
Aerosol Generation, Monitoring, and
Collection ................ 12
Extraction of Aerosol Products ......... 12
Extraction Procedures ........... 13
Fractionation of Aerosol Extracts ........ 14
Fractionation Procedures .......... 15
Derivatization of Aerosol Products ....... 15
Preparation of Dithiolane Derivatives ... IQ
Preparation of Perf luoroester Derivatives . 19
Preparation of Phosphate Derivatives. ... 19
Analysis of Aerosol Products by Gas
Chromatography and Mass Spectrometry ...... 20
Gas Chroma to graphic and Mass Spectral
Procedures . ............... 23
IV RESULTS AND DISCUSSION ..... ........ 24
Smog Chamber Irradiations ............ 24
Extraction of Aerosol Products ......... 24
Fractionation of Aerosol Extracts ........ 28
Derivatization of Aerosol Products ....... 29
IV
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CONTENTS
Page
Dithiolane Derivatives of Authentic Carbonyl
Compounds 28
Dithiolane Derivatives of crPinene and
Cyclohexene Aerosol Products 31
Perfluoroacyl and Phosphate Derivatives of
Authentic Alcohols 41
Phosphate Derivatives of crPinene Aerosol
Products 44
Analysis of Cyclohexene Aerosol 50
Cyclohexene Aerosol Acid Fraction 50
Cyclohexene Aerosol Neutral Fraction 57
Cyclohexene Aerosol Basic Fraction 65
Analysis of Toluene Aerosol 65
Toluene Aerosol Acid Fraction 65
Toluene Aerosol Neutral Fraction 74
Analysis of cr-Pinene Aerosol 79
cr-Pinene Aerosol Acid Fraction 81
crPinene Aerosol Neutral Fraction 90
Studies Based on Known Reactions of
a-Pinene 94
Tentative Assignments for orPinene
Neutral Products. ... 109
crPinene Basic Fraction 116
REFERENCES 125
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FIGURES
No. paSe
1 Gas Chromatograms of Authentic Dithiolanes 32
2 Reconstructed Gas Chromatograms of Authentic Dithiolanes 33
3 Chemical lonization Mass Spectra (Methane) of Authentic
Dithiolanes 34
4 Chemical lonization Mass Spectra (Methane) of Authentic
Dithiolanes 35
5 Chemical lonization Mass Spectra (Methane) of Authentic
Dithiolanes 36
6. Analysis of Cyclohexene Aerosol, Neutral Fraction Dithiolane
Derivatives. Reconstructed Gas Chromatogram for Methane
CT-MS 38
7 Analysis of ^-Pinene Aerosol, Neutral Fraction Dithiolane
Derivatives. Reconstructed Gas Chromatogram for Methane
CI-MS 39
8 Analysis of Cyclohexene Aerosol, Neutral Fraction Dithiolane
Derivatives. Chemical lonization Mass Spectrum (Methane)
for Chromatographic Peak A. (Refer to Chromatograms in
Figure 6) 40
9 Analysis of Cyclohexene Aerosol, Neutral Fraction Dithiolane
Derivatives. Chemical lonization Mass Spectrum (Methane)
for Chromatographic Peak B. (Refer to Chromatogram in
Figure 6) 43
10 Reconstructed Gas Chromatogram of Diethylphosphate
Derivatives of Authentic Alcohols 45
11 Chemical lonization Mass Spectra (Methane) of
Diethylphosphate Derivatives of Authentic Alcohols 46
12 Chemical lonization Mass Spectra (Methane) of
Diethylphosphate Derivatives of Authentic Alcohols 47
13 Analysis of ry-Pinene Aerosol, Neutral Fraction
Diethylphosphate Derivatives. Reconstructed Gas Chromato-
gram for Methane CI-MS 48
14 Analysis of ry-Pinene Aerosol, Neutral Fraction Diethylphos-
phate Derivatives. Chemical lonization Mass Spectrum
(Methane) for Chromatographic Peaks A and B. (Refer to
Chromatogram in Figure 13) 49
VI
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FIGURES
(Continued)
No.
15 Analysis of Cyclohexene Aerosol, Acid Fraction Methyl
Esters. Reconstructed Gas Chromatogram for Methane
CI-MS 51
16 Analysis of Cyclohexene Aerosol, Acid Fraction Methyl
Esters. Chemical lonization Mass Spectrum (Methane)
for Chromatographic Peak C. (Refer to Chromatogram in
Figure 15) 52
17 Analysis of Cyclohexene Aerosol, Acid Fraction Methyl
Esters. Chemical lonization Mass Spectrum (Methane)
for Chromatographic Peak A. (Refer to Chromatogram in
Figure 15) 53
18 Analysis of Cyclohexene Aerosol, Acid Fraction Methyl
Esters. Chrmical lonization Mass Spectrum (Methane)
for Chromatographic Peak B. (Refer to Chromatogram in
Figure 15) 54
19 Analysis of Cyclohexene Aerosol, Acid Fraction Methyl
Esters. Chemical lonization Mass Spectrum (Methane)
for Chromatographic Peak D. (Refer to Chromatograms in
Figure 15) 56
20 Analysis of Cyclohexene Aerosol, Neutral Fraction.
Reconstructed Gas Chromatogram for Methane CI-MS 58
21 Analysis of Cyclohexene Aerosol, Neutral Fraction.
Reconstructed Gas Chromatogram for Helium CI-MS 59
22 Analysis of Cyclohexene Aerosol, Neutral Fraction.
Chemical lonization Mass Spectra for Chromatographic
Peak A. Spectrum I by Methane CI-MS, Spectrum 2 by
Helium CI-MS. (Refer to Chromatogram in Figure 21) 61
23 Analysis of Cyclohexene Aerosol, Neutral Fraction.
Chemical lonization Mass Spectra for Chromatographic
Peak B. Spectrum 1 by Methane CI-MS, Spectrum 2 by
Helium CI-MS. (Refer to Chromatogram in Figure 21) 63
24 Analysis of Cyclohexene Aerosol, Neutral Fraction,
Chemical lonization Mass Spectra for Chromatographic
Peak D. Spectrum 1 by Methane CI-MS, Spectrum 2 by
Helium CI-MS. (Refer to Chromatogram in Figure 21) 64
25 Analysis of Toluene Aerosol, Acid Fraction Methyl Esters/
Ethers. Reconstructed Gas Chromatogram for Methane CI-MS 66
vn
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FIGURES
(Continued)
No.
26 Analysis of Toluene Aerosol, Acid Fraction Methyl Esters/
Ethers. Chemical lonization Mass Spectrum (Methane) for
Chromatographic Peak B. (Refer to Chromatogram in
Figure 25) 67
27 Analysis of Toluene Aerosol, Acid Fraction Methyl Esters/
Ether. Chemical lonization Mass Spectrum (Methane) for
Chromatographic Peak A. (Refer to Chromatogram in
Figure 25) 70
28 Analysis of Toluene Aerosol, Acid Fraction Methyl Esters/
Ethers. Chemical lonization Mass Spectrum (Methane) for
Chromatographic Peak C. (Refer to Chromatogram in
Figure 25) 71
29 Analysis of Toluene Aerosol, Acid Fraction Methyl Esters/
Ethers. Chemical lonization Mass Spectrum (Methane) for
Chromatographic Peak D. (Refer to Chromatogram in
Figure 25) 72
30 Analysis of Toluene Aerosol, Acid Fraction Methyl Esters/
Ethers. Chemical lonization Mass Spectrum (Methane) for
Chromatographic Peak E. (Refer to Chromatogram in
Figure 25) 73
31 Analysis of Toluene Aerosol, Neutral Fraction. Recon-
structed Gas Chromatogram for Methane CI-MS 75
32 Analysis of Toluene Aerosol, Neutral Fraction. Chemical
lonization Mass Spectrum (Methane) for Chromatographic
Peak B. (Refer to Chromatogram in Figure 31) 76
33 Analysis of Toluene Aerosol, Neutral Fraction. Chemical
lonization Mass Spectrum (Methane) for Chromatographic
Peak F. (Refer to Chromatogram in Figure 31) 77
34 Analysis of Toluene Aerosol, Neutral Fraction. Chemical
lonization Mass Spectrum (Methane) for Chromatographic
Peak A. (Refer to Chromatogram in Figure 31) 78
35 Analysis of Toluene Aerosol, Neutral Fraction. Chemical
lonization Mass Spectrum (Methane) for Chromatographic
Peak E. (Refer to Chromatogram in Figure 31) 80
36 Analysis of o'-Pinene Aerosol, Acid Fraction Methyl Esters.
Reconstructed Gas Chromatogram for Methane CI-MS 82
vi 11
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FIGURES
(Continued)
No.
37 Analysis of a-Pinene Aerosol, Acid Fraction Methyl Esters.
Chemical lonization Mass Spectrum (Methane) Corresponding
to Methyl Pinonate. (Refer to Chromatogram in Figure 36) 83
38 Chemical lonization Mass Spectrum (Methane) of Authentic
Methyl cis-Pinonate 84
39 Analysis of cv-Pinene Aerosol, Acid Fraction Methyl Esters.
Reconstructed Gas Chromatogram for Methane CI-MS 87
40 Analysis of o/-Pinene Aerosol, Acid Fraction Methyl Esters.
Chemical lonization Mass Spectrum (Methane) for Chromato-
graphic Peak A. (Refer to Chromatogram in Figure 39) 88
41 Analysis of Blue Ridge Mountain Aerosol, Acid Fraction
Methyl Esters. Reconstructed Gas Chromatogram for Methane
CI-MS 91
42 Analysis of Blue Ridge Mountain Aerosol, Acid Fraction
Methyl Esters. Chemical lonization Mass Spectrum (Methane)
Corresponding to Pinonic Acid. (Refer to Chromatogram in
Figure 41) 92
43 Analysis of a-Pinene Aerosol, Neutral Fraction. Recon-
structed Gas Chromatogram for Methane CI-MS 95
44 Reconstructed Gas Chromatograms of Authentic Terpenoids 98
45 Chemical lonization Mass Spectra (Methane) of Authentic
Limonene and Terpinolene 99
46 Chemical lonization Mass Spectra (Methane) of Authentic
o-Fenchyl Alcohol and Borneol 100
47 Chemical lonization Mass Spectra (Methane) of Authentic
crTerpinol and Myrtenal 101
48 Chemical lonization Mass Spectra (Methane) of Authentic
Terpin Hydrate and Fenchone 102
49 Chemical lonization Mass Spectra (Methane) of Authentic
trans-Verbenol 103
50 Chemical lonization Mass Spectra (Methane) of Myrtenol
and Carveol 104
51 Analysis of a-Pinene Aerosol, Neutral Fraction. Chemical
lonization Mass Spectrum (Methane) for Chromatographic
Peak E. (Refer to Chromatogram in Figure 43) 106
IX
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FIGURES
(Continued)
No.
52 Analysis of crPinene Aerosol, Neutral Fraction. Chemical
lonization Mass Spectrum (Methane) for Chroraatographic
Peak C (Refer to Chromatogram in Figure 43) 107
53 Analysis of a-Pinene Aerosol, Neutral Fraction. Chemical
lonization Mass Spectrum (Methane) for Chromatographic
Peak B. (Refer to Chromatogram in Figure 43) 108
54 Analysis of a-Pinene Aerosol, Neutral Fraction. Chemical
lonization Mass Spectrum (Methane) for Chromatographic
Peak A. (Refer to Chromatogram in Figure 43) 110
55 Analysis of a-Pinene Aerosol, Neutral Fraction. Chemical
lonization Mass Spectrum (Methane) for Chromatographic
Peak F. (Refer to Chromatogram in Figure 43) 114
56 Analysis of a-Pinene Aerosol, Neutral Fraction. Chemical
lonization Mass Spectrum (Methane) for Chromatographic
Peak G. (Refer to Chromatogram in Figure 43) 116
57 Analysis of rrPinene Aerosol, Neutral Fraction. Chemical
lonization Mass Spectrum (Methane) for Chromatographic
Peak D. (Refer to Chromatogram in Figure 43) 117
58 Analysis of a-Pinene Aerosol, Neutral Fraction. Chemical
lonization Mass Spectrum (Methane) for Chromatographic
Peak H. (Refer to Chromatogram in Figure 43) 118
59 Analysis of a-Pinene Aerosol, Basic Fraction. Reconstructed
Gas Chroroatogram for Methane CI-MS 120
60 Analysis of a-Pinene Aerosol, Basic Fraction. Chemical lon-
ization Mass Spectrum (Methane) for Chromatographic Peak A.
(Refer to Chromatogram in Figure 59) 121
61 Analysis of crPinene Aerosol, Basic Fraction. Chemical
lonization Mass Spectra for Chromatographic Peak B
Spectrum 1 by Methane CI-MS, Spectrum 2 by Helium CI-MS.
(Refer to Chromatogram in Figure 59) 123
62 Analysis of a-Pinene Aerosol, Basic Fraction. Chemical
lonization Mass Spectrum (Methane) for Chromatographic
Peak C. (Refer to Chromatogram in Figure 59) 124
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TABLES
No. Page
1 Summary of Irradiation Conditions and Smog
Parameters 25
2 Solvent Extraction of Collected Aerosol 26
3 Fractionation of Methylene Chloride Extractable Matter 29
4 Rationalized Fragmentation of Authentic Methyl
Pinonate Under Conditions of Chemical lonization
Mass Spectrometry (Methane) 35
5 Rationalized Fragmentation of Tentatively Identified
Methyl Pinononate Under Conditions of Chemical
lonization Mass Spectrometry (Methane) 89
XI
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SECTION I
SUMMARY AND CONCLUSIONS
This study has been directed toward detailed organic chemical char-
acterization of aerosols generated from individual hydrocarbon pre-
cursors under simulated atmospheric conditions. Model aerosols
were generated using the Battelle-Columbus Laboratories' 17.3 m
environmental chamber. Systems studied during this program include
cyclohexene/NOx, toluene/NOx, and o/-pinene/NOx. Aerosol was collect-
ed on glass-fiber filters and organic matter was obtained by sequential
solvent extraction. Reaction products were fractionated into acid,
neutral, and basic components and were analyzed in detail by techniques
including gas chromatography and gas chromatography combined with
mass spectrometry (GC-MS). Additionally, techniques were evaluated
for the selective derivatization of aerosol products. This was
directed at "tagging" specific functional groups with easily
detectable markers. Overall, the objective of the analytical effort
was the identification of individual reaction products formed from
each hydrocarbon precursor. By comparing the structure of such
products with the parent hydrocarbon, and with each other, we may
infer the types of organic reactions occurring under atmospheric
conditions.
Tentative identification of a variety of aerosol products has been
accomplished. The results of this study are best summarized by
reference to these products. In considering the structures shown
below it should be emphasized that these are tentative identifications.
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Cyclohexene aerosol.
COOH
CHO
COOH
CHO
COOH
CH2OH
COOH
p o
TENTATIVE CH3-CH =CH -C -C -(
CYCLOHEXENE
CHO
CHO
HO-CH2-CH2-CH=CH-CH=CH2
or
CHO
or
CHO ~l
Toluene aerosol.
CH,
O
TENTATIVE
COOH
.CH2OH
CH3
TOLUENE
COOH CH2OH
OH
(TWO ISOMERS)
CH,
CHO
OR
HO
CH
CHO
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a-Pinene aerosol.
COOH
TENTATIVE
a-PINENE
COOH
CHO
CHO
In view of the reaction conditions, formation of many of the above
aerosol products is not particularly surprising. Oxidative cleavage
of carbon-carbon double bonds is to be expected in an ozone con-
taining atmosphere. Oxidative decarboxylation and formation of
alcohols, carboxylic acids and carbonyl compounds is consistent
with free radical processes expected in the atmosphere. Neverthe-
less, exnerimental demonstration of the formation of such products
should be of value.
The fate of nitrogen oxides in the atmosphere has long been a ques-
tion of interest. In this context, the current research has included
identification of two classes of nitrogen-containing products.
Nitrate esters were tentatively identified in cyclohexene aerosol,
and aromatic nitro compounds were tentatively identified in toluene
aerosol. This infers that nitration of an aromatic ring is occur-
ring under atmospheric simulation. Identification of such nitrate
esters and nitropenols is of interest from the standpoints of both
fundamental atmospheric chemistry and health effects.
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In studying model aerosols, it is often possible to characterize
reaction products more easily than if these products were present
in the more complex mixture of atmospheric organics. Moreover,
identification of interesting compound types in model aerosol suggests
that such compounds may be present in atmospheric aerosol. For
example, during earlier phases of this research the formation of
5-nitratopentanoic acid was reported. Subsequently, such nitrate
esters were identified in atmospheric aerosol during elegent mass
(1)**
spectral studies of Schuetzle, Crittenden, Cronn, and Charleson
Thus, characterization of model aerosols is complementary to and
supportive of research directed toward characterization of atmospheric
aerosol.
An ultimate objective of model aerosol research is the development
of a comprehensive basis for predicting the types of products that
can be expected to form when specified organic compounds are re-
leased into the atmosphere. Needless to say, this objective remains
quite distant. It is hoped that the results of this study have con-
tributed to the attainment of that goal.
*See Background and Introduction section.
**References are listed on page 125.
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SECTION II
BACKGROUND AND INTRODUCTION
It is by now well established that the aerosols which form as a
result of photochemical smog reactions are composed predominantly
of organic matter. Because of the complexity of smog formation
little is known of the pathways by which organic vapors undergo
chemical change to become aerosols. The ultimate objective of this
research program is the elucidation of organic chemical reactions
involved in such aerosol formation. An understanding of these pro-
cesses would allow us to predict the types of aerosol products that
would be formed from a particular pollutant. Moreover, a comprehensive
understanding of such reactions might allow us to assign sources con-
tributing to the atmospheric hydrocarbon burden.
Analysis of atmospheric particulate matter reveals a complex mixture
of organic components. Similarly, the organic vapors emitted into
the atmosphere, the compounds that fuel photochemical aerosol form-
ation, also represent a highly complex mixture. It is not surprising,
therefore, that it has been difficult, if not impossible, to corre-
late observed components of atmospheric particulate with specific
organic pollutants or well-defined organic reactions. In view of
this complexity, thi;i research has been based on the study of simple
and controllable model aerosol systems.
Many model studies have examined the factors influencing aerosol
formation, and the time course of this phenomenon. These
studiesC^-^/J have considered such parameters as NOX concentra-
tion, S02 concentration, relative humidity, and stirring of
reactants within the chambe". The aerosol-forming tendency
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(28 29)
of various hydrocarbons has similarly been evaluated. ' Research
concerned with the mechanism of aerosol forme
i
microscopic examination of aerosol particles
concerned with the mechanism of aerosol formation has involved electron
(30,31)
In contrast to such studies, the research reported herein has been
directed toward characterization of specific aerosol reaction products
formed from individual hydrocarbons. Few studies have involved de-
/ 1 Q O 1) \
tailed characterization of this type. ' A notable exception
is the model aerosol research conducted during the first year of the
(34) *
program "Haze Formation--Its Nature and Origin" . This program
sponsored jointly by the Environmental Protection Agency (CPA 70-Neg
172) and the Coordinating Research Council (CAPA 6-68) was the direct
predecessor of the current study. For the sake of clarity and
completeness, salient aspects of that study are included in this
report.
"Research concerning composition of model aerosols conducted during
the "Haze Formation" study was supported in part by Grant AP-00828
from the Office of Research Grants, EPA. The principal investigator
was William E. Wilson.
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SECTION III
RATIONALE AND METHODS OF PROCEDURE
Despite the reduced complexity of model aerosols compared to atmospheric
aerosol, the reaction mixtures generated during atmospheric simulation
are indeed complex. Thus, the analytical scheme employed was designed
to reduce this complexity and simplify characterization of individual
reaction products.
During the first year of this study, emphasis has been placed on
characterization of aerosol products that have not undergone ex-
tensive oxidation or degradation. Identification of such compounds
is profitable in that the products characterized can be more easily
related to the parent hydrocarbon. On the basis of this relationship
we may infer the types of reactions occurring under atmospheric
simulation. The extraction and fractionation procedures described
below were designed to separate the reaction mixture into defined
components with varying degrees of oxidation/degradation. Detailed
analyses were conducted using the less degraded fractions of the
reaction mixture.
It is recognized that many interesting and significant products may
be present in the more highly oxidized fractions. Indeed, such pro-
ducts are more abundant than the less degraded components. Although
the first year's study has emphasized characterization of the less
oxidized reaction components, future work vill include analysis of the
more highly oxidized materials.
Under the headings below, further rationale concerning the experi-
mental approach is discussed, and methods of procedure are described.
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SELECTION OF HYDROCARBON PRECURSORS
Toluene, o-pinene, and cyclohexene were selected as precursors for
the generation of model aerosols. Selection was based on a number
of criteria. First, it was desired to include hydrocarbons of various
classes, and where feasible, to select members of these classes which
represent important contributors to the atmospheric hydrocarbon burden,
Also taken into account was the aerosol reactivity of candidate hydro-
(35)
carbons . Hydrocarbons having high aerosol reactivity were favored
in view of the need to obtain sufficient aerosol mass for analysis.
All hydrocarbons studied to date in this program are active aerosol
formers. Future work will include compounds of more limited reac-
tivity, such as branched alkanes.
Inspection of early morning hydrocarbon distribution data in both
East and West^ ' Coast cities indicates that aromatic hydro-
carbons comprise between 30 and 40 percent of the nonmethane hydro-
carbon. Of these, toluene is the most abundant, comprising approxi-
mately 25-40 percent of the total aromatics. Study of this compound
permits us to observe the behavior of both an aromatic ring, and an
alkyl substituent under conditions of atmospheric simulation.
It has been reported that approximately 175 million tons of reactive
hydrocarbons are released into the atmosphere annually from tree
foliage sources^38*39). This is over sixfold greater than the
estimated 27 million tons released from technological sources. The
major compounds released by plants and trees are the monoterpenes
(CIQ), and the semiterpene isoprene (65). It has been speculated
that the natural "blue haze" observed in many forested regions arises
from the atmospheric reactions of these compounds. o"Pinene, chosen
for use in this study, is one of the principal monoterpenes emitted
(38,39)
from these sources
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Selection of cyclohexene was made on a somewhat broader basis. The
above-cited studies of early morning hydrocarbon distribution in
East and West Coast cities indicates that olefins comprise between
10 and 20 percent of the total nonmethane hydrocarbon. Olefins
having four or more carbon atoms comprise about 25 percent of the
total olefin fraction. Smog chamber studies have demonstrated
that such olefins have considerable propensity to form organic
aerosols, the aerosol-forming tendency increasing with the molecular
weight of the olefin. Although cyclohexene is rarely detected in
urban atmospheres, this compound is known to be a particularly prolific
aerosol precursor. This stems in part from the fact that cleavage
of the cyclohexene double bond leads to formation of bifunctional
oxidation products. Compared to monofunctional products formed from
acyclic olefins, these bifunctional products have decreased volatility
and greater tendency to enter the aerosol phase. In view of the
desireability of obtaining high aerosol mass loadings, cyclohexene
was selected for study.
GENERATION OF MODEL AEROSOLS
3
Model aerosols were generated using the Battelle-Columbus 17.3 m
environmental chamber. In selecting the conditions for aerosol genera-
tion, it was necessary to strike a compromise between the desire to
operate at the relatively low reactant concentrations typically observed
in authentic atmosphere, and the need to provide sufficient aerosol mass
for organic analysis. Typically, -10 ppm (vol/vol) hydrocarbon was used.
Nitrogen oxide concentrations ranging from 2-5 ppm (NO + N0£) were
employed, and were selected and adjusted to obtain reaction kinetics
typical of photochemical smog manifestations. Preliminary runs were
conducted to determine suitable reactant concentrations for each aerosol
system studied.
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The reactant concentrations employed are at least an order of
magnitude greater than atmospheric levels. The effect of the higher
reactant concentrations on the aerosol chemistry is uncertain. In
general, however, most of the chemical reactions responsible for
smog formation are first order inreactants, and the first encounter
an intermediate has with another potentially reactive species is
nearly always with oxygen molecules. Therefore, only in instances
where the overall speed of radical-radical reactions approaches that
of radical-02 reactions will the overall reaction pathways of inter-
mediates be seriously affected by the higher concentration of react-
ants. Judging from the small fraction of reactions meeting this
condition, it is believed that the concentrations employed did not
result in a serious departure from normal smog chemistry. This
argument, of course, is oversimplified; however, until a detailed
understanding of aerosol reaction mechanisms is developed further,
speculation on the importance of concentration in these simulations
is unwarranted.
Smog Chamber Characteristics
The smog chamber utilized in these studies is approximately 2.4 m
high, 4.9 m long, and 1.5 m wide, having a volume of approximately
17.3 m . The surface-to-volume ratio is 0.78. The inside surface
9 9
consists of 35.3 m of polished aluminum and 9.2 ra of FEP-
Teflon windows (5 mil thick) through which the reaction mixture
is irradiated using an external bank of lamps. The lamp bank
consists of 96 fluorescent "black" lamps and 15 fluorescent
sunlamps. The spectral distribution of the black lamps peaks in
intensity at 370 nm; the sunlamps peak intensity occurs at 310 nm.
Light intensity generated corresponds to a k< of 0.45 min as deter-
mined by NOo photolysis and o-nitrobenzaldehyde actinometry. This
intensity is comparable to that of noonday sun over the wavelength
integral of NC>2 absorption.
10
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Air supplied to the chamber is taken in through a 10-m stack atop
a three-story building, and is passed through a purification system
including a permanganate filter bed, a charcoal filter system, an
absolute filter, and a humidification unit. After purification,
background total-hydrocarbon is generally 1-3 ppmC with the majority
of this being methane. A trace of background ethane is occasionally,
observed by gas chromatography. Olefins and aromatics have
always been below gas chromatographic detection limits. Sulfur
dioxide is always below the detection limit of a flame photometric
detection (~10 ppb) and carbon monoxide background levels are
generally between 1 and 3 ppm as measured by nondispersive infrared
spectroscopy. Light scattering readings are essentially the same
as for clean air (Raleigh scattering) and the condensation nuclei
count is generally less than 200 particles per cubic centimeter.
Smog-Chamber Cleanup
Prior to each series of experiments with a different model hydro-
carbon, it was necessary to thoroughly clean the chamber's surface
to prevent cross contamination of aerosol products. Such cross
/ f\ I \
contamination had been observed during previous studies . Cleanup
was accomplished by washing down chamber surfaces with a spray of
4:1 isopropanol:water. Prewashed cloths were used to scrub the sur-
faces and surgical scrub suits were worn to prevent contamination
from street clothing. Throughout the procedure, the chamber was main-
tained on purge (8500 1 min ). Nevertheless, the high concentration
of solvent vapor that develops, requires that the chamber be sealed
and that the worker be provided with an auxiliary breathing apparatus.
After cleanup, the chamber was purged overnight and was then per-
mitted to stand with 1 ppm ozone for several hours. Before genera-
tion of aerosol for analytical use, a "conditioning" run was conducted
using the model system to be studied.
11
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Aerosol Generation. Monitoring, and Collection
Detailed data concerning reactant concentrations and conditions are
shown in Table 1 (p. 25 ). After initial concentrations were estab-
lished, the mixing fan was turned off and irradiation was begun.
Parameters monitored throughout the course of the experiment included
NO and NC>2 concentration using a continuous Saltzman analyzer, total
hydrocarbon concentration using a flame ionization detector, ozone
concentration using a chemiluminescence analyzer, and light scatter-
ing using an integrating nephelometer.
In general, irradiation was continued until light scattering measure-
ments indicated that maximum aerosol growth had occurred. After
this maximum was observed, irradiation was halted and the aerosol
was collected by evacuating the chamber contents through tared
10-cm-diaraeter glass-fiber filters (Gelman Type A) using a high-
f\
volume type sampler. Typically, about 11 m of chamber volume
was sampled over a 30-minute period. Before use, the filters were
washed repeatedly, first with distilled-in-glass methanol, and then
with methylene chloride. They were then equilibrated at 50 percent
R,H. and tared. After collection, the filters were reequilibrated,
weighed, and placed in glass containers for storage at -60 C. After
a series of runs was completed, collected aerosol was subjected to
Soxhlet extraction, as described below.
EXTRACTION OF AEROSOL PRODUCTS
Collected aerosol was subjected to Soxhlet extraction first with
methylene chloride, and then with either acetone or methanol. The
sequential extraction procedure was used in order to obtain reaction
products having a wide range of oxidation state and polarity. The
methylene chloride extracts are expected to contain products less
oxidized than those obtained in the metbanol or acetone extracts.
12
-------
Thus, consistent with previously discussed rationale, the methylene
chloride extractable matter was used for subsequent detailed analysis.
Extraction with the more polar solvent was conducted in order to
provide a measure of weight-percent extractable into solvents of
varying polarity, and to obtain the more oxidized reaction products
for possible analysis during future work. Values for weight-percent
extractable (see Results and Discussion section) should be valuable
in that they permit comparisons of data for model aerosols with
that obtained for atmospheric aerosol.
It should be emphasized that samples were collected on prewashed
filters. Soxhlet extraction of such prewashed filters was con-
ducted, and blank values for weight-percent extractable were deter-
mined.
Extraction Procedures
All extractions were conducted using high-purity "distilled-in-glass"
solvents (obtained from Burdick and Jackson, Muskegon, Michigan).
Methylene chloride extractions were run for 20 hours; methanol or
acetone extractions were run for 44 hours. Approximately 25 ml of
solvent was used for each 10-cm-diameter filter disk. The volume of
extract was reduced to 1-3 ml using a Kuderna-Danish fractionating
column. In order to determine values for weight-percent extractable,
a small aliquot (~1 percent) of the concentrated extract was taken
to dryness on a light (~5 mg) aluminum weighing pan. Pans were
tared and reweighed using a Cahn Electrobalance, and aliquot .
weights were determined to ± 2 (ig. From these data the total weight
of extractable matter was calculated. Values for weight-percent
solvent extractable were calculated as shown below. In making these
calculations a correction was made to account for filter blank.
13
-------
Weight-percent _ (weight of extracted matter, corrected)
solvent extractable (weight of total participate)
FRACTIONATION OF AEROSOL EXTRACTS
As noted previously, detailed analyses were conducted using methylene
chloride extractable matter. In order to simplify the analytical
task, the extractable matter was fractionated according to the scheme
below.
Methylene Chloride Extractable Matter
Water-Soluble Fraction Water-Insoluble Fraction
I
Acid Neutral Basic
Fraction Fraction Fraction
The water-insoluble fraction can be expected to contain the relatively
less oxidized, less degraded components of the reaction mixture.
In keeping with the previously expressed objective of this phase of
the study, detailed analyses were conducted using the water-insoluble
fraction. Further fractionation into acid, neutral, and basic com-
ponents was performed in order that analyses could be conducted using
mixtures partially defined according to chemical class. For example,
in analyzing a neutral fraction, one might anticipate the presence
of aldehydes, ketones, or alcohols, but not carboxylic acids or
phenols.
14
-------
Fractionatlon Procedures
The methylene chloride extractable matter was fractionated into
water-soluble and water-insoluble components by extracting the
methylene chloride solution (~3 ml) four times with 2 ml por-
tions of distilled water. All extractions were conducted in
conical centrifuge tubes agitated using a vortex mixer. This
procedure permits convenient centrifugation of emulsions prior to
separation of phases, and minimizes sample losses. Water was re-
moved by lyopholization, and the weight of the water-soluble
fraction was determined.
The water-insoluble material remaining in solution was next extracted
four times with ~2-ml portions of 2N aqueous sodium hydroxide and
twice with ~2-ml portions of distilled water. The sodium hydroxide
and water washes were combined.
The methylene chloride solution was then extracted three times with
~2-ml portions of 2N hydrochloric acid and twice with ~2-ml portions
of distilled water. The acid and water washes were combined. Addi-
tional water washes were made until neutral; these were discarded.
Material remaining in methylene chloride solution after extraction
with both aqueous sodium hydroxide and hydrochloric acid is defined
as the water-insoluble neutral fraction.
The sodium hydroxide extract (containing organic-acid salts) was
brought to pH ~0.1, and the free acid was extracted into methylene
chloride using a continuous liquid/liquid extractor for 96 hours.
Similarly, the hydrochloric acid extract (containing organic-base
salts) was brought to pH ~13, and the free base was extracted into
methylene chloride, again using a continuous liquid/liquid extractor
for 96 hours. The methylene chloride solutions containing the acid,
15
-------
basic and neutral fractions were dried by refluxing the solutions
over a 3-A molecular sieve. Drying the solutions directly with
anhydrous magnesium sulfate or molecular sieve was found to be
unsatisfactory because of irreversible adsorption of organics upon
the drying agent.
The dried solutions were concentrated to a volume of -1 ml using a
Kuderna-Danish fractionating column. The weight of organic matter
in the concentrated solutions was determined by taking an aliquot
of the concentrate (~5 percent) and evaporating the solvent on a
light (~5-mg) aluminum weighing pan. Pans were tared and reweighed
using a Cahn Electrobalance, and aliquot weights were determined to
±2 u,g. Using values determined for the weights of the vario'us frac-
tions, weight percent distribution values were calculated.
DERIVATIZATION OF AEROSOL PRODUCTS
In order to aid product characterization, the program included study
of selective derivatization of aerosol reaction products. This was
directed at "tagging" specified functional groups with easily
detectable markers. This is useful in that the mass spectral data
often do not permit unambiguous identification of the functional
groups in a sample. It is especially true where gas chromatography
combined with mass spectrometry is performed at unit resolution T
such cases the empirical formula cannot always be determined with
certainty. Thus, a study of selective derivatization was under-
taken to assess the usefulness of this approach to aerosol
characterization.
Specific derivatization of carbonyl groups and hydroxyl groups was
investigated. Derivatization of carbonyl groups was conducted by
reaction with ethanedithiol to form corresponding dithiolane" as
shown in the reaction below.
16
-------
V
HS
- - " /\ _
Carbonyl ,CH2 S 2
compound HS ^--i.- i
K Dithiolane
Ethanedithiol derivative
Dithiolanes can be selectively detected using flame-photometric gas
chroma tography. Additionally, they produce distinctive fragmentation
patterns upon mass spectrometric analysis.
Various reagents for derivatization of hydroxyl groups were investi-
gated, including
II X^t
1. Trifluoroacetyl imidazole, CFo C N N
oW
il X^
2. Heptaf luorobutyryl imidazole, C^F-7-C-N N
o
II
3. Heptaf luorobutyryl chloride, C-jFy-O
0
II
4. Pentaf luorobenzoyl chloride, C^F^-C-
0
II
5. Diethylchlorophosphate, (C2H50)2P-Cl
The fluorinated acyl chloride and acyl imidazole reagents react with
hydroxyl functions to form fluorinated ester derivatives. These can
be selectively detected by electron-capture gas chromatography,
0
P
R(F)-C-G1 0
or 0 + ROH - ^ R(F)-C-OR
li
R(F)-C-IM
17
-------
Diethylchlorophosphate reacts with hydroxyl groups to form the cor-
responding phosphate ester.
M °
(C2H50)2P-C1 + ROM ». (C2H50)-P-0R
Such derivatives can be selectively detected by flame-photometric
gas chromatography. Thus, the phosphates can be analyzed using the
same instrument and detector as is used for analysis of the dithio-
lanes. Like dithiolanes, phosphates produce strikingly characteristic
mass spectral fragmentation patterns.
Finally, it should be noted that, prior to the analysis of the acid
fraction by gas chromatography and GC-MS, it was treated with diazo-
methane. This commonly used reagent converts carboxylic acids and
phenols to relatively volatile methyl esters and methyl-aryl ethers,
thereby permitting gas chromatographic analysis.
Preparation of Dithiolane Derivatives
The procedure employed for preparation of dithiolanes was adapted
from methods reported by Fieser ' and by Corey et al. ' Typically
1-10 mg of an authentic carbonyl compound or aerosol product was mix-
ed with 0,5 ml of ethanedithiol and 0.5 ml of distilled BFo-etherate
in a 3-ml reaction vial with Teflon-lined screw-cap. The reaction
mixture was heated at 60 C overnight. It was then cooled and diluted
with 5-10 ml of "distilled-in-glass" methylene chloride. The methy-
lene chloride solution was then washed twice with an equal volume
of distilled water, three times with 10 percent aqueous sodium hy-
droxide, and again, twice with distilled water. Extractions were
conducted in conical centrifuge tubes agitated using a vortex-
mixer. This permits convenient centrifugation of emulsions prior
to separation of phases.
18
-------
After the above cleanup, the tnethylene chloride solution was dried
by refluxing over molecular sieve (3A), and the dried solution was
concentrated to a volume of 1 ml using a Kuderna-Danish fraction-
ating column. The concentrate was retained for analysis by gas
chromatography and GC-MS.
Preparation of Perfluoroester Derivatives
Preparation of perfluoroester derivatives of alcohols was conducted
using reagents 1-4 above and was performed according to a procedure
(43)
adapted from Pierce Chemical Company product literature . Typically,
2 mg of authentic alcohol or aerosol product was mixed with 200 M-l
of dry pyridine in a 1-ml reaction vial with Teflon-lined screw cap.
To this was added ^200 mg of acyl chloride or acyl itnidazole reagent.
Combination of reactants was conducted in a glove bag under dry
nitrogen. The reaction mixture was then heated at 60 C for 2-6 hours.
Workup of the reaction mixture was begun by slowly adding 1 ml of
ice cold distilled water to destroy excess reagent. The mixture was
extracted three times with 2-ml portions of chilled "distilled-in-
glass" hexane. Extractions were conducted in a conical centrifuge
tube agitated using a vortex mixer. The hexane solution was dried,
concentrated and retained for analysis by electron-capture gas
chromatography.
Preparation of Phosphate Derivative^
The derivatization procedure was adapted from methods reported by
(44} (45)
Corey and by Brown . Typically, 2-20 mg of authentic alcohol
or aerosol product was combined with 0.5 ml of dry 2,6-lutidine and
0.25 ml of diethylchlorophosphate in a 3-ml reaction vial with Teflon-
lined cap. The vessel was closed securely and the mixture was heated
to 60 C for 30 min, and was then permitted to stand at room temp-
erature overnight.
19
-------
Workup of the reaction mixture was begun by slowly adding 1 ml of
distilled water to destroy excess reagent. The mixture was then
washed into a conical centrifuge tube using ~5 ml of distilled-in-
glass methylene chloride. The solution was extracted once with
~3 ml of distilled water, three times with IN hydrochloric acid
once again with distilled water, three times with IN aqueous sodium
bicarbonate, and finally, twice with distilled water. All wash
solutions were chilled in an ice bath before use, and extractions
were conducted using a conical centrifuge tube agitated by means of a
vortex mixer.
After workup, the methylene chloride solution was dried by re-
fluxing over 3-A molecular sieve. It was then concentrated to 1 ml
using a Kuderna-Danish fractionating column. The concentrate was
retained for analysis by gas chromatography and GC-MS.
ANALYSIS OF AEROSOL PRODUCTS BY GAS CHROMATOGRAPHY
AND MASS SPECTROMETRY
After extraction, fractionation, derivatization, and preliminary
analysis by gas chromatography, the aerosol reaction products were
analyzed by gas chromatography combined with mass spectrometry.
Analyses were performed using a quadrupole mass spectrometer. The
ion source of this instrument has been modified to permit generation
of either chemical ionization or electron impact mass spectra. Most
of the analyses conducted during this study were performed in the
chemical ionization mode.
During the last several years there has been a marked increase in
use of chemical ionization mass spectrometry. Nevertheless, it is
probably less familiar to many analytical chemists than conventional
electron impact spectrometry. Since a considerable number of chemical
ionization spectra are presented in this report, some of the basic
20
-------
characteristics of the technique are reviewed briefly below.
In chemical-ionization spectrometry , the sample molecules are ion-
ized by means of vapor state interaction with ions of a "reactant
gas". The reactant gas most commonly used is methane. As shown
in the reaction sequence below, the methane is ionized by electron
impact causing formation of a series of primary ions. At pressures
of about 1 torr, these react further with methane to produce the
secondary ions shown. These secondary ions are the principal species
present in the ion source of the spectrometer
CH<1 e~ ^CH4+ CH3+ METHANE ^ CH5+ C2H5+
CH2+ CH+ -1TORR
PRINCIPAL SPECIES
The secondary ions cause ionization of the sample molecules by donat-
ing a proton or abstracting a hydride ion. As shown in the reactions
below, this interaction leads to formation of quasimolecular ions
having mass/charge (m/e) one unit greater than or one unit less
than the molecular weight (M) of the sample molecule. The quasi-
molecular ions are almost always observed; generally they are prominant,
ROH2 +
ROM ~"~ \
U QUASIMOLECULOR IONS
ALCOHOL _ +^>. J+
SAMPLE C2H5 ^ RO -i-
21
-------
There is also a tendency for the sample molecule to form an adduct
with the C2H5 ion or the C3H5 ion. When this occurs "satellite
ions" are observed at m/e values corresponding to M + 29 and M + 41
The observation of the quasimolecuiar ion and satellite ions facilitates
the assignment of molecular weight. During this study use of GC-MS
has thus permitted tentative assignment of molecular weights for the
majority of principal chromatographic peaks in a sample.
In general, chemical ionization mass spectra show a great deal less
fragmentation than electron impact spectra. In addition, the frag-
ment ions that are observed generally arise from elimination of
functional groups as small neutral molecules. Thus, chemical ion-
ization spectra are often easier to correlate with structural features
than are electron impact spectra.
In some cases chemical ionization spectra were obtained using helium
as the reagent gas. Helium ions are species of much higher energy
than the secondary ions of methane. The resulting spectra show far
more fragmentation than those obtained using methane. The helium
spectra are, in fact, very similar to classical electron-impact
spectra. Generation of both methane and helium chemical-ionization
spectra often aids in characterizing the sample.
Finally, it should be emphasized that the mass spectral characteriza-
tions presented in this report are almost invariably referred to
as "tentative". Firm identifications can only be made when reference
spectra are available for comparison. In view of the relatively
recent advent of chemical-ionization mass spectrometry extensive
compilations of such reference spectra are unavailable. Thus in
many instances authentic compounds were obtained, and reference
spectra determined in attempts to confirm tentative assignments.
22
-------
This approach was used extensively during analysis of the a-pinene
aerosol.
The interpreted spectra shown in the report include varying numbers of
significant peaks which have not been rationalized. Many such peaks
arise from the presence of contaminating compounds which elute simul-
taneously with the assigned product. In analysis of complex mixtures
by GC-MS many spectra will show such contributions from multiple
components.
Gas Chromato^rapjiic and Mass Spectral Procedures
Gas chromatographic separations were performed using a 3-m x 2-mm-
ID (1/4-in-OD) Pyrex column packed with 3 percent OV-17 on Gas Chrom
Q. Typically, analyses were performed with temperature programming,
100 - 250 C at 4 C/min. Two dual detector chromatographs were used
in the study, a Varian Model 1700 equipped with flame-photometric
detector and flame-ionization detector, and a Varian Model 2100
equipped with electron-capture detector and flame-ionization detector.
Analysis by GC-MS was performed using a Finnigan 1015 Mass Spectro-
meter. Instrument control and data acquisition were accomplished using
a System Industries 150 data acquisition system. The reconstructed
gas chromatograms shown in this report were computer generated. The
detector response in these chromatograms was derived from the total
ion current observed during successive scans on the spectrometer.
Typically in this study, scans were repeated every 8 seconds. Thus,
the x-axis of a reconstructed gas chromatogram is roughly equivalent
to retention time. Desired spectra are recalled from computer memory
(disk) by reference to the spectrum number.
23
-------
SECTION IV
RESULTS AND DISCUSSION
SMOG CHAMBER IRRADIATIONS
Irradiation conditions and smog manifestations characterizing the model
aerosols are shown in Table 1. The values listed represent averages for
the respective hydrocarbon series. There was very little run-to-run
variation in the parameters; the magnitude of such variation was insuf-
ficient to be of any consequence to the composite aerosol composition.
In general, the smog reactions in both the cyclohexene andcx-pinene se-
ries were very fast as evidenced by the rapid rate of NO photooxidation
(Table 1, NO -, values). The NO photooxidation rate in the toluene se-
ries was considerably less in spite of the higher HC/NO ratio employed.
3t
These trends in relative hydrocarbon reactivity toward NO photooxidation
are similar to those reported in the literature.^ '
EXTRACTION OF AEROSOL PRODUCTS
Collected aerosol was subjected to sequential solvent extraction. Cyclo-
hexene aerosol was extracted first using methylene chloride and then
acetone. Toluene and ct-pinene aerosols were extracted first using methyl-
ene chloride and then methanol. Values for weight-percent solvent ex-
tractable are shown in Table 2.
As noted previously, collections were made using prewashed glass fiber
filters. In calculating values shown in the table, filter background
(blank) has been subtracted. Soxhlet extraction of prewashed filters
gave blank values of 0.007 mg per 10-cm-diameter disk for methylene
chloride extraction and 0.27 mg per 10-cm-diameter disk for methanol ex-
traction.
It is interesting to compare valuer shown in the table with those of
weight-percent extractable observed for atmospheric particulate matter,
24
-------
TABLE 1. SO1MARY Op I RRAOMTION1 C.OSDt TI ('.\S AM) SMOC PARAMETEKS ' 3
Hvdroca r hon
Cvc lohexone To 1 uene T_-1' i neiu-
( b)
Number ot runs 2
1 rrad iat ion pe r i od , in i n 180
Relat i ve humid ily
Initial, percent <>4
Final, percent 5h
Hydrocarbon
Mass I rrad iated , g
initial concentration, ppm C
Final concentration, ppm C;'c'
N i i r ic ox i de
Initial concentration, ppm
l, .,. mi./1"
1/2
NitrogL-n dioxide
Initial concentration, ppm
Maximum concentration, ppm
Ozone
Maximum concentration, ppm
t , inin
max
(e)
Light scattering
Maximum, 10 m
Mass loading , mg m
Percent conversion
(3)
Total aerosol mass collected, g
O.«04
63
2U
2.4
15
2.4
4.8
0.46
180
I 10
1 3.0
28.0
0. 390
0 . * '-> 7 1 . ^ 2 1
71 104
Ml Ji,
1.0 J . 0
75 ii
1.2 J . 0
1.4 i . 0
0.7 O.OOh
34 35
180 220
1.4 33
2.8 40
0.125 1.341
(a) Data shovn are averages for (he series o; runs, except lor values ol total
aerosol mass collected, t'hich represent the toial mass collected during an
entire series of runs.
(b) After conditioning, a series of [our cvclohexcne runs was conducted.
Aerosol from li.'O of the runs was compromised during work-up.
( c ) Includes L on t r i hu t i on t r»>m prt>tl uc t I o rma L ion.
(d) Time at which one half the initial amount i>( \() wa s oxidised to Xl > ; .
(e) Indic;iLeil values are outside the/ normal operating ran^e ol ttie inlenrating
nephe1omet er.
(1) Mass loading was calculated by dividing the aerosol mass collected l>^ the
ell'ective volume sampled. 'Hie effective volume sampled was calculated hv
measuring the decrease in total organic carbon during the sampling period
and multiplying this fractional decrease Iv. t'ie chamher volume.
(g) Percent conversion i-'as calculateil as total aerosol mass per mass ol
hydrocarbon i r rail ial ed. Total aerosol mass va s calculated 1 rom the
indicated mass loading multiplied In- t lie claniln-r volume ol 17.3 m .
25
-------
Table 2. SOLVENT EXTRACTION OF COLLECTED AEROSOL
0s-
=====
Hydrocarbon
Cyclohexene
Toluene
a-Pinene
=====
Total
Aerosol
Mass
Extracted,
g
0.390
0.125
1.341
.
First Extraction,
Weight-Percent
Methylene Chloride
Extractable
62
46
92
ii' -
r~:
Second Extraction
Solvent
Acetone
Methanol
Methanol
Weight-Percent
Solvent Extractable
31
43
1
Total Extractable
Matter,
Weight-Percent
93
89
93
!
-------
such as those reported in the second annual report on "Haze Formation --
Its Nature and Origin" . During that study, atmospheric particulate
matter was collected in Columbus, Ohio, New York City, and Pomona
California. It was similarly subjected to solvent extraction first using
methylene chloride, and then dioxane. (Dioxane was used as the polar
solvent in order to minimize extraction of the considerable quantities
of inorganic salts known to be present in atmospheric particulate.) Re-
ported values for methylene chloride extractable average 15 weight per-
cent, ranging from 8-22 weight percent. Values for dioxane extractable
average 21 weight percent, ranging from 8-40 weight percent. Values for total
extractable average 36 weight percent, ranging from 16-56 weight percent.
Comparison of these values with those shown in Table 2 indicates that
the model aerosols contain significantly more organic extractable matter
than do atmospheric aerosols. This is especially evident when comparing
values for methylene chloride extractable matter. The data support the
contention that aerosols which form as a result of photochemical reactions
are composed predominantly of organic matter.
In considering the structures of the hydrocarbon precursors, it is in-
teresting to note that as the total number of carbon atoms per double-
bond decreases there is a tendency for the reaction products to have
less solubility in methylene chloride and greater solubility in the polar
solvent, that is, acecone or methanol (see structures p. 28).
The data suggest that under atmospheric simulation, hydrocarbons having
increased numbers of double-bonds will undergo greater oxidation/
degradation, yielding products which would be expected to have greater
solubility in solvents of greater polarity (i.e., acetone or methanol
rather than methylene chloride).
^Strict reference is made to'"double-bonds" rather than "unsaturation"
because the bicyclic compound a-pinene has unsaturation equivalent to a
monocyclic hydrocarbon containing two double bonds.
27
-------
a-PINENE
CARBON ATOMS PER DOUBLE-BOND
(10)
CYCLOHEXENE
(6)
CH,
TOLUENE
(2.3)
FRACTIONATION OF AEROSOL EXTRACTS
Using the procedure described previously, methylene chloride eytractable
matter was fractionated into water-soluble and water-insoluble components
The water insoluble material was further fractionated into acid, neutral
and basic components. The distribution of reaction products in the three
aerosol systems is shown in Table 3.
DERIVATIZATTON OF AEROSOL PRODUCTS
Procedures for specific derivatization of alcohols and carbonyl compounds
were investigated and the utility of this approach was considered as an
aid to identification of aerosol reaction products. The various deriva-
tization reagents described earlier were evaluated using model alcohols
and carbonyl compounds, and selected reagents were applied to derivati-
zation of reaction products.
Dithiolanes of Authentic Carbonyl Compounds
Using the previously described derivacization procedure, dithiolanes of
the following authentic carbonyl compounds were prepared: n-hexaldehyde
n-heptaldehyde, 2-ethylhexaldehyde, 2-ethyl buteraldehyde, 3-hexanone,
and 2,4-dimethyl-3-hexanone. The gas chromatographic retention times of
the dithiolanes are significantly longer than those of the parent
28
-------
Table 3. FRACTIONATION OF METHYLENE CHLORIDE EXTRACTABLE MATTER
Hydrocarbon
Cyclohexene
Extractable Matter Fractionated, mg 80
Water- insoluble fraction
Acid, weight percent
Neutral, weight percent
Basic, weight percent
Water-soluble fraction, weight percent
Overall recovery, weight percent
8
3
0.2
66
77
Toluene ct-Pinene
29 615
10 52
2 17
0.3 1
70 27
82 97
-------
carbonyl compounds. For example using a 3-m x 2-mm 3% OV-17 column pro-
-.]_ K
grainmed from 100 to 250 C at 6 C min the retention time of 3-hexanone
and 2-ethylbuteraldehyde dithiolanes are 9.3 and 11.0 minutes respec-
tively, whereas both parent compounds elute in less than 2 minutes. Gas
chromatograms of several authentic dithiolanes are shown in Figure 1
Both flame ionization and flame photometric (sulfur specific) detection
were employed. The dithiolanes were further analyzed by GC-MS. Recon-
structed gas chromatograms are shown in Figure 2, and chemical-ionization
mass spectra are shown in Figures 3-5.
Fragmentation of aldehyde dithiolanes is highly characteristic and is
clearly diagnostic of the presence of aldehyde in the original aerosol
product mixture. The fragmentation is rationalized below, and includes
formation of the diagnostic fragment at m/e 105.
RCH = SH
R C CH2
V
RCH
X
HS-CH2
'S-CH2
LOSS OF
PROTONATED
MOLECULAR
ION
LOSS RH
-SCH,
CH
DIAGNOSTIC FRAGMENT
m/e = 105
Fragmentation of ketone dithiolanes is similarly characteristic, but
does not include appearance of the fragment at m/e 105. This can be
helpful in distinguishing aldehyde and ketone dithiolanes. Fragmenta-
tion of the ketone dithiolanes is rationalized below.
30
-------
R C
LOSS OF
'C=SH
CH2- CH2
Dithiolane Derivatives of a-Pinene
and Cyclohexene Aerosol Products
Portions of the o.-pinene and cyclohexene neutral fractions were reacted
with ethanedithiol/BF^ to obtain dithiolane derivatives. The deriva-
tized product mixtures were analyzed by gas chromatography and GC-MS.
For the sake of clarity mass spectral analyses of the derivatized
aerosol products are considered as a unit under this heading. Analyses
of unde.rivatized aerosol products are considered separately in following
sections for each of the three aerosol systems studied. In the present
discussion, the analytical approach involving dithiolane derivatives
will be evaluated.
Analyses of dithiolane derivatives for both rv-pinene and cyclohexene
aerosol products indicated the presence of carbonyl compounds whose
molecular weights were rather low when compared to the compounds which
were identified in the underivatized neutral fractions. In the cyclo-
hexene neutral fraction, analyses of the dithiolanes indicated the
presence of carbonyl compounds of the following molecular weights:
76, 84, 96, 98, 108, and 112. The a-pinene neutral fraction was
31
-------
KETONE DITHIOLANES
ALDEHYDE DITHIOLANES
N O
Z O
LU LJJ
5 0
B
12 MINUTES
0 3 6 9 12 15 MINUTES
cc
LU
LU Q
DITHIOLANE DERIVATIVES OF:
A. 3-HEXANONE
B. 2.4-DIMETHYL-3-HEXANONE
C. n-HEXALDEHYDE
D. n-HEPTALDEHYDE
E. 2-ETHYLHEXALDEHYDE
SAMPLES ANALYZED USING A
10 FT x 2 MM COLUMN OF
3-PERCENT OV-17 ON GAS
CHROM Q TEMPERATURE
PROGRAMMED 100-250°C
AT6°C/MIN
FIGURE 1. GAS CHROMATOGRAMS OF AUTHENTIC DITHIOLANES.
-------
U)
OJ
DITHIOLANE DERIVATIVES OF:
A. n-HEXALDEHYDE
B. n-HEPTALDEHYDE
C. 2-ETHYLHEXALDEHYDE
D. 3-HEXANONE
E. 2-ETHYLBUTYRALDEHYDE
F. 2,4-DIMETHYL-3-HEXANONE
10 28 30
6PECTRH KJCEB
90
FIGURE 2. RECONSTRUCTED GAS CHROMATOGRAMS OF AUTHENTIC DITHIOLANES.
-------
F
R.
S_
?-
JR_
R_
c
o
(
. ^S-CH2
CH | _^
, , T*l
111, U>
^CH3lCH2i4CH = SH
^ '
II
lilt,..)!.,,,.,! ,1.1
X \
CH2-CH?_
ll 1
lUv -,X^.T- 1
, n-HEXALDEHYDE
DITHIOLANE
V
E
I
5
o ^
E E
^ ^i
u V
2 £
m« T i-i'-i
SO 70 90 30 100 110 120 130
MX
ISO 160 170 ISO 190 200 210 220 230 2« 2SO 2BB 270 290 230
R.
~
\&-<
9
sR.
B.
D
,-H'' "TZ
,
JU.i rtt
LnlJ,
n HEXALDEHYDE
DITHIOLANE
-tH-j-'CHjij -CH ~SH
S
CH? ~tHJ
-
1 ^
-
II,,
=
I
II. . .
SO 70 80 98 100 110 120 130 110 ISO :60 170 190 190 208 2lO 220 230 210 250 268
MX E
FIGURE 3. CHEMICAL IONIZATION MASS SPECTRA (METHANE)
OF AUTHENTIC DITHIOLANES.
(Refer to Chromatograms in Figure 2}
34
-------
2-ETHYLHEXALDEHYDE
DITHIOLANE
GO 70 88 30 100 110 120 130 110 ISO 168 170 180 130 2BB 210 220 230 210 2GO 2SB 278 280 2
8_
-
~
CH, - CH, - CH, - - C - CH, - C
3-HEXANONE DITHIOLANE
ll| llllit'l'lllilltdUl''"'""!"11!""!1'"!""! ,l [iiiumi) iii.i.ny.
80 39 100 110 128 130 110 ISO ICO 179 160 130 59
! I I I I1
210 22B 230 210 2
CO 70
FIGURE 4. CHEMICAL IONIZATION MASS SPECTRA (METHANE)
OF AUTHENTIC DITHIOLANES.
(Refer to Chromatograms in Figure 2)
35
-------
b6L
R_
2-ETHYLBUTYRALDEHYDE DITHIOLANE
J
so' V '«'"»" IBB iio 'i»"iai»T« ' iso in 'ITS 'ise
MX e
g
RJ
r-*
IK
R-l
(. CHiLH-, ^
2,4-DIMETHYL-3-HEXANONE DITHIOLANE
SB 'TO w M ino 'ne IZB
Y« 'l ISO iTB 188 IS) MB 219 OB 238 Z« Z9B ZBO 270 ZBO 230 3BB
FIGURE 5 CHEMICAL IONIZATION MASS SPECTRA (METHANE)
OF AUTHENTIC DITHIOLANES.
(Refer to Chromatograms in Figure 2)
36
-------
indicated to contain carbonyl compounds of molecular weights, 44, 76,
78, 90, 104, and 108. The reconstructed gas chromatograms are shown
in Figures 6 and 7.
Analysis of the underivatized neutral fraction of cyclohexene aerosol
indicates possible formation of the products indicated below. (See
mass spectra in Figures 22 and 23. These spectra are discussed in
detail under the headiag Cyclohexene Neutral Fraction.)
0 ° run
n ii LHO
CH3-CH = CH-C-C-CH3
(MW =112) (MW = 96)
Mass spectra of the derivatives indicate the presence of dithiolanes
corresponding to carbonyl compounds having the above molecular weights,
112 and 96 (peaks A and B in Figure 6). Consider the mass spectrum
shown in Figure 8. This dithiolane corresponds to a derivative formed
f'.-om carbonyl of molecular weight 112. Although the intense peak at
m/e = 189 appears to correspond to the protonated molecular ion
(dithiolane), the other rather weak peaks are not consistent with a
xSx
ketone. The weak peak at m/e = 129 (loss of CH2~CH2) would be expected
for both aldehydes and ketones, but the relatively strong peak at
m/e = 105 is usually diagnostic for aldehydes.
In contrast, the mass spectrum for the underivatized product suggests
the diketone, above. If the assignment of the diketone structure is
correct, then the derivative mass spectrum in Figure 8 indicates the
presence of an aldehyde which was not identified in the cyclohexene
neutral fraction. Since this derivative spectrum gives little evidence
regarding the parent carbonyl compound, any structure suggested would
be purely speculative. The empirical formula is most probably
C6H802.
37
-------
P.
8
8_
to
9 18 20 JO -W
SPECTHLfl MJ«EB
60 70 80 <» 180 118 120 138 HO ISO 160 170 180 130 ZOO 210 22O Z3B ZtO ZS5
U>
OO
GIVEN IN PARENTHESIS IS THE
MOLECULAR WEIGHT OF THE
CARBONYL COMPOUND
CORRESPONDING TO THE
(A)
ii
g
5
J
A . .-,
/
FIGURE 6. ANALYSIS OF CYCLOHEXENE AEROSOL, NEUTRAL FRACTION DITHIOLANE DERIVATIVES.
RECONSTRUCTED GAS CHROMATOGRAM FOR METHANE CI-MS.
-------
u>
6
"" 1
R_
8_
P.
8.
I
JR.
j
*D
R.
R.
o
1
GIVEN IN PARENTHESIS IS THE
MOLECULAR WEIGHT OF THE
CARBONYL COMPOUND
CORRESPONDING TO THE
INDICATED DITHIOLANE
3
S
7
i n
1 ft
vUL__
; i i I I pi '<"! i i"'
00
r>
<«
<£>
s
<*l
SI
I
?
oo 3
o o
Sao o
00 ffl
« ffl "
C '-P
1 s i I !
P A1 ft UAA^
All ^/^^JULJ^^IU^^
'. _ . . » . -« < -j« t «A i o» i CH t -?n i an t qn ?nrt ? i (1 77ft y.n j-w ,Oii3 SO ^70 iflfl S30
0 18 28 30 10 SO 60 70 80 30 JOB HO IZB
3PEETBJ1 «>BEP
FIGURE 7. ANALYSIS OF a-PINENE AEROSOL, NEUTRAL FRACTION DITHIOLANE DERIVATIVES.
RECONSTRUCTED GAS CHROMATOGRAM FOR METHANE CI-MS.
-------
R.
0>
o
CM
0)
1
CM
. CM
X
u
§
0)
-^
68 73
-------
Consider the mass spectrum shown in Figure 9. This dithiolane corre-
sponds to a derivative formed from carbonyl of molecular weight 96.
The peak at m/e 173 corresponds to the protonated parent ion. The
-S-
peak at m/e 113 corresponds to loss of CH2~CH2 . The complete absence
of a peak at m/e 105 would suggest that the parent compound may be
a ketone. However, we have been unable to explain the other strong
peaks at m/e = 89, 101, and 119 in these terms. It is possible that
these fragments represent interference arising from other compounds
simultaneously eluted. Thus, it is not clear whether the dithiolane
corresponds to a derivative of the indicated aldehyde, or to a deriva-
tive of a carbonyl compound that was not otherwise detected in the
cyclohexene neutral fraction.
Dithiolane derivatives of the o-pinene neutral fraction were prepared
and analyzed by GC-MS. No carbonyl compounds found in the a-pinene
neutral fraction corresponded with the rather low molecular weight
derivatives found. The absence of higher molecular weight carbonyl
derivatives may indicate that these species failed to elute under the
chromatographic conditions employed, as there is no clear reason why
they should not be formed.
In conclusion, it appears that use of dithiolane derivatives is a
potentially useful approach to aid in characterization of carbonyl
reaction products. In order to utilize this approach, gas chroma-
tographic conditions will be determined which permit elution of the
higher molecular weight dithio lanes.
Perf luoroacyl and Phosphate Derivatives
of Authentic Alcohols
For convenience, the previously described candidate reagents for deri-
vatization of alcohols are listed below:
41
-------
1. Trifluoracetyl imidazole
2. Heptafluorobutyryl imidazole
3. Heptafluorobutyryl chloride
4. Pentafluorobenzoyl chloride
5. Diethylchlorophosphate.
Evaluation of Reagents 1-3 indicated that although the desired esters
are formed with various model alcohols, the product esters are in-
sufficiently stable and are hydrolyzed back to free alcohol and
perfluorocarboxylic acid during aqueous work-up of the reaction mix-
ture. Gas chromatographic analyses of the reaction mixtures without
aqueous work-up proved to be troublesome in that excess derivatization
reagent was deposited at the head of the GC column, leading to column
degradation and irregular results.
Reagent 4 was shown to be sufficiently reactive toward various primary
and secondary alcohols. Excess reagent was easily hydrolyzed during
work-up without decomposition of product esters. The product esters
were shown to be suitable for specific detection by electron-capture
gas chromatography.
Simultaneous with evaluation of Reagent 4, diethylchlorophosphate,
Reagent 5, was studied. This reagent has properties similar to those
of the carboxylic acid chlorides, and was shown to react with various
primary and secondary alcohols. Reaction with a tertiary alcohol
(3-methyl-3-hexanol) was also attempted, but no product was observed
by gas chromatography. The phosphate derivatives produced can be
specifically detected using flame-photometric gas chromatography.
Thus preliminary analysis of such alcohol derivatives can be conducted
using the same instrument as is used for analysis of dithiolane deri-
vatives of carbonyl compounds. In view of this fact, evaluation of
diethylchlorophosphate was emphasised.
42
-------
U'
s.
h«1
VI-
CM
X
CO
03
CO
-------
Phosphate derivatives of various primary and secondary alcohols were
prepared and analyzed by GC-MS . A reconstructed gas chromatogram for
the derivatives of isopropanol, 1-pentanol, 3-hexanol, and 1-decanol
is shown in Figure 10. The mass spectra are shown in Figures 11 and 12.
A clearly characteristic fragmentation pattern is evident in the spectra.
It appears that initial fragmentation of the phosphate ester involves
loss of olefin corresponding to the parent alcohol. Subsequent frag-
mentation was identical for all of the derivatives, and simply involved
two successive losses of ethylene.
0 0 0 o
+ " LOSS OF + " LOSS OF + " LOSS OF II
H P (OC2H5)2 - H P (OC2Ha)2 H - H P-OC2H5 H P(OH)3
z4
OR OH (OH)2
Phosphate Derivatives of a-Pinene
Aerosol Products
A portion of the a-pinene neutral fraction was derivatized with
diethylchlorophosphate, and was analyzed by GC-MS. The reconstructed
gas chromatogram is shown in Figure 13. The chromatographic resolution
of the derivatives is poor. Examination of typical spectra shown in
Figure 14 reveal very characteristic phosphate fragmentation with
peaks at m/e 155, 127, and 99. It was nevertheless, not possible to
identify significant parent or adduct peaks in these spectra. Con-
sequently, the molecular weight of the products could not be determined.
Examination of spectra of authentic phosphate derivatives indicates
that even when a strong protonated parent ion is observed, fragmentation
is rather uninformative. At best, it appears that preparation and
analysis of phosphate derivatives can aid in establishing the presence
of alcohol and the molecular weight of an aerosol product. In light of
these findings, this approach to specific derivatization of alcohols
was discontinued. Limited future work may be undertaken using Reagent 4
above.
44
-------
t_n
8
8-
8.
A
DIETHYLPHOSPHATE DERIVATIVES OF
A.
B.
C.
D.
ISOPROPANOL
n-PENTANOL
3-HEXANOL
n-DECANOL
0 10 ZO 30
SPECTHLH WJBEH
SC 6C 7C 80 3C 1
ilC 1ZC 13C 1
15C !60 170 180 130 "JK '.
ZX i-W 2SO 260
FIGURE 10. RECONSTRUCTED GAS CHROMATOGRAM OF DIETHYLPHOSPHATE
DERIVATIVES OF AUTHENTIC ALCOHOLS.
-------
8
8_
O
HP(OHI3
-C2H4
OH
HP^o
OH
HP- OH
\
IOC,H
DERIVATIVE OF
ISOPROPANOL
2"5'r
7C 8C B8
130 IKJ ISO
)70
Z3B ilff 220 230
^^_
R_
8_
f~
if-
ML
|*~
y. -
8~
0
D_
J
OH
HP OH
(OH)j lu">2
O
HP'OH
68 70 SO
3
\
X
as
O(
\ /
2\*
3B
C2H4
*
,
1 T
1«5 M
i»
IOC2H5I2
\*
_^l~^l
,1 ll
S
3 1ZB 135 I'M »3J !S5 175 IP!? ;3C
I
., 1
DERIVATIVE OF
1-PENTANOL
fSl
Psi
T
*c. _n
X I
CN n
LJ u
2 ^
M/ f """'
FIGURE 11. CHEMICAL ION1ZATION MASS SPECTRA (METHANE) OF
DIETHYLPHOSPHATE DERIVATIVES OF AUTHENTIC ALCOHOLS.
(Refer to Chromatogram in Figure 10)
46
-------
. 13
0
HPlOH(3
DERIVATIVE OF
3-HEXANOL
OH
HP - OH
NOTE THfc WfAK PARENT
ION FOR THIS Df RIVATIUE
OF a SECONDARY ALCOHOL
60 76 SB 88 tBO iM 121 138 VK ISO 160 178 18(5 I9O 355 ZlO 23S 230 Z*S ZSO 2BO
n/ E
290 30B 318 320 330
8
5L
8.
K
i
R-
t^
'" "" !
(OHI2
HP - O
O
HP - OH
\
o
HP (OMI3
\ \
\ ^
\
^
C2H4
^ CjM,
2 6?
.-
!. , .
- -I111"' -! I1 1,1.1.,... IIll.,... ,....,1. ..... ,..! Il..,.c -,.. , ,..
'" T'
DERIVATIVE
1-DECANOL
r
» .« 1 If* 1O*« ^31» <
OF
C2M,
»A( 9O*
C2M4
I..I
R
E
"r
, 1 1
sen 5T« 5qn ;«« am _3is 32B 3
e=0 7C 9S 3D 100
n/ e
FIGURE 12. CHEMICAL IONIZATION MASS SPECTRA (METHANE) OF DIETHYLPHOSPHATE
DERIVATIVES OF AUTHENTIC ALCOHOLS.
(Refer to Chromatogram in Figure 10)
-------
oo
5r~ST"S"" 70 90 30 100 110 120 130 110 ISO 160 170 190 190 200
FIGURE 13 ANALYSIS OF a-PINENE AEROSOL, NEUTRAL FRACTION DIETHYLPHOSPHATE DERIVATIVES.
RECONSTRUCTED GAS CHROMATOGRAM FOR METHANE CI-MS.
-------
V
R-
S.
»
J
E8'
58 .
JR.
8.
o
1
0
4- "
HP(OH)3
^^
2*
P 1 1 "1 1"*1
B TO «B 3D 100 IK
Hit
"-,
R.
8.
P -
8n
8-
toS_
I*'
R
o
«
-t-
HP
O
HP(OH)3
1
V -
:2
*4
HP v
^-^"
(OH)2
/
/
0
V H FRACTION A
OC2H5 OH
+ /
-C2H4
) 120 130
OH
/
0
\
OC2H5
\
H4
i ;
i i i i"""1
-
HP 0
(OC2H5)2
i j J iVi..,!i 1 , .'.-... i. . i, . . . . . i i i ' i i i i i i
IKS ise 'ise \ie J«B las ZBB ZIB ZZB zao 'z« as zse zro ao ae see a>o szo aw >»
C2H4
^T"^1"!
(OH}2
4 /
HP - 0
->,oc2H5>2 FRACTION B
,, ,r,
ea TO to 3D 100 110 izo iao
Hlf
FIGURE 14. ANALYSIS OF a-PINENE AEROSOL, NEUTRAL FRACTION DlETHYLPHOSPHATE DERIIV'ATIVES.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAKS A AND B.
(Refer to Chromatogram in Figure 13)
-------
ANALYSIS OF CYCLOHEXENE AEROSOL
Cyclohexene Aerosol Acid Fraction
The water-insoluble acid fraction of cyclohexene aerosol was isolated as
described above. The mixture was treated with diazomethane, and the
resulting methyl esters were analyzed by gas chromatography and GC-
MS. The reconstructed gas chromatogram is shown in Figure 15. Tentative
identifications have been made on the basis of mass spectra for the
indicated chromatographic components.
The mass spectrum corresponding to chromatographic peak C is shown
in Figure 16. The product is tentatively identified as the six membered
aldehyde-acid shown. There is a moderately strong peak assigned as
protonated parent ion at m/e 145. Fragmentation peaks consistent
with loss of CH30H and loss of CH3CHO are observed at m/e 113 and
101j respectively. Somewhat less prominent is a peak corresponding
to loss of HCOOCH3 (methyl formate). This can be seen at m/e 85.
Loss of HCOOCH3 and CH3
-------
muni ntinpiiijiiii|iiiijiiiniiii[Mii|i'i'iinniiin i
0 10 20 30 10 SO 60 70 60 98 100 11Q 120 13C
SPECTRM NUr«SR
FIGURE 15. ANALYSIS OF CYCLOHEXENE AEROSOL, ACID FRACTION METHYL ESTERS.
RECONSTRUCTED GAS CHROMATOGRAM FOR METHANE CI-MS.
-------
Ul
ro
g
-
D
O
TENTATIVE
ASSIGNMENT:
C
CHO
,,.
4
t+7
o
II
O
fi
X
+TTf
in
sf
I
TyTTTipTTTfTTTT,,,,,!,,,,,.,,,!,,,.,} ^ IT^TJTTTT^TTJTTTTT, ,,.r,. f,, , ,,, ...,r,Mf,T,rT,,r,1,,r.
10 S0 60 70 00 30 100 110 120 130 110 ISO 160
M/ E
FIGURE 16. ANALYSIS OF CYCLOHEXENE AEROSOL, ACID FRACTION METHYL ESTERS.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK C.
(Refer to Chromatogram in Figure 15)
-------
B
OO
O
FIGURE 17.
1
1 5
"
I ^
+ '
0
o
z
TENTATIVE
£ °» ASSIGNMENT.
0 '
± j; . COOCH3
1
4fl 5fl GO 70 80 90
\
> CHO
CO
u
E ft
+~ 7
I
- t
"in
CM
O
i
,H|,1|.,, |.|...| .Illlllll |1llllMM| l|l -J+T-T
100 110 120 130 HO ISO 'l6C 173
M/ E
ANALYSIS OF CYCLOHEXENE AEROSOL, ACID FRACTION METHYL ESTERS.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK A.
(Refer to Chromatogram in Figure 15)
-------
TENTATIVE
ASSIGNMENT:
COOCH3
CH2OH
70
90
'iST UO 120 133 'HO ISO 160 170 193
B.
(Refer to Chromatogram in Figure 15)
-------
at m/e 161 is consistent with adduct ion (M f 02^) . Prominent
fragmentation peaks consistent with loss of H£0 and loss of C^OH
are observed at m/e 115 and 101 respectively, while the less intense
peak at m/e 73 corresponds to loss of HCOOCH3.
Finally, consider the mass spectrum shown in Figure 19, corresponding
to chromatographic peak D. This rather interesting product is
tentatively identified as the 5-nitrate ester of the product considered
in the case above. The peak for protonated parent-ion is observed at
m/e 178. Prominent fragmentation peaks consistent with loss of
CHoOH and loss of HN03 are observed at m/e 146 and 115, respectively.
In summary, four bifunctional carboxylic acids indicated below have
been tentatively identified in the acid fraction of cyclohexane aerosol,
Oxidative cleavage of cyclohexane in the presence of ozone and hydrogen
peroxide can reasonably be expected to yield 6-oxohexanoic acid.
(Hydrogen peroxide has been observed in the atmosphere and in model
systems '°1)_) Further oxidative decarboxylation might then yield the
5-oxopentanoic acid. The 5-hydroxypentanoic acid might be formed via
disproportionation from pentanedialdehyde.
6-OXOHEXANOIC 5-OXOPENTANOIC 5-HYDROXYPENTANOIC 5-NITRATOPENTANOIC
ACID ACID ACID ACID
Formation of 5-nitratopentanoic acid is of interest for a number of
reasons. First, the presence of nitrate esters in the atmosphere could
be significant from the standpoint of health effects. In general,
-------
(Jl
g
H
8_
8.
v£O
£
jjp-
&D
L0_
So
§
EO
SB
D
fcL
0
TENTATIVE
ASSIGNMENT:
CCOOCH3
s.
CH2ONO2
\ I1"
10 SO
i
l''»|'"'|..i., , ,
60 70 GO SO 1
\, i, ,,],,]
in
£
ii
'a>
1
-t- *
o1
I
i
§
I 0
I3""
u ."
§ "s
ii
00
1
"E
+ *
i
i
00 110 120 130 140 ISO 160 170 160 13
M/ E
FIGURE 19. ANALYSIS OF CYCLOHEXENE AEROSOL, ACID FRACTION METHYL ESTERS.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK D.
(Refer to Chromatograms in Figure 15}
-------
the fate of nitrogen oxides in the atmosphere has long been a question
of interest. Formation of nitrate esters represents an additional
"nitrogen sink" in the atmosphere. Currently there is considerable
controversy regarding the formation mechanism of peroxyacylnitrate
(PAN) in the atmosphere. Nevertheless, it is interesting to speculate
as to possible formation mechanism for nitrate esters. This might
involve the formation of a charge transfer complex between the olefin
and N02> which would result in enhanced reactivity of the vinyl
hydrogen. A+
CYCLOHEXENE - N02 CHARGE TRANSFER COMPLEX
One can speculate that free radical oxidation could result in a peroxy
species at the vinyl hydrogen, and it is possible that a concerted
induced homolytic peroxy fission followed by addition of the complexed
NC>2 could result in a nitrate ester. This suggested mechanism is
somewhat similar to that previously proposed for cyclic sulfite formation
from olefins and sulfur dioxide' '. It is also possible that the
mechanism is entirely free radical in nature, as has been suggested
for PAN formation. However, in the absence of additional supportive data,
further mechanistic suggestions appear to be unwarranted.
Cyclohexene Aerosol Neutral Fraction
The water insoluble neutral fraction of cyclohexene aerosol was isolated
as described previously, and was analyzed by gas chromatography and
GC-MS. Both methane and helium chemical ionization spectra will be
considered. The reconstructed gas chromatogram for methane CI is
shown in Figure 20; that for helium is shown in Figure 21.
57
-------
00
10 20 30
SPEETFU1
10 SO 60 70 90 3B
"t |""l"ii| 1 ;ini|iiii| i | .j.u.,.,11, ;»IHIIIHMI.|II»I
100 110 120 130 110 ISO 160 170 180 190 200 210 22C
230 2*
260
280
328
310
380 330
FIGURE 20. ANALYSIS OF CYCLOHEXENE AEROSOL, NEUTRAL FRACTION.
RECONSTRUCTED GAS CHROMATOGRAM FOR METHANE CI-MS.
-------
Ul
vD
T 1
13 28 JB «
3TCTFl> MJflFH
-WO
SOB SIO
FIGURE 21. ANALYSIS OF CYCLOHEXENE AEROSOL, NEUTRAL FRACTION.
RECONSTRUCTED GAS CHROMATOGRAM FOR HELIUM CI-MS.
-------
It should be pointed out that chromatographic peaks C and E represent
the only notable case of contamination observed during this year's
study. The two components have been identified as dimethyl gluturate
and dimethyl adipate. Although the source of contamination remains
uncertain, these two compounds are widely used industrial plasti-
cizers. Glutaric or adipic acids might be expected in the acid
fraction but should not appear in the neutral fraction. Moreover,
the neutral fraction was never treated with diazome thane, thus methyl
esters could not have been formed from aerosol products.
Of the neutral aerosol products for which possible structures have
been presented, the most interesting is considered in Figure 22.
This mass spectrum corresponds to chromotographic peak A. The several
structures shown are consistent with both the methane and helium
chemical ionization spectra. The methane spectrum suggests a com-
pound of molecular weight 96. Peaks are observed consistent with
parent ion, protonated parent ion, and parent minus hydride ion at
m/e 46, 97, and 95 respectively. Peaks consistent with adduct ions
are observed at m/e 125 and 137 (M + C2H5) and M + C-jH^) . In the
helium mass spectrum peaks are observed consistent with parent ion
at m/e 96, and respectively, loss of H, HCO, and (HCO + C2H^) from
the parent ion, at m/e 95, 67, and 39, respectively.
As indicated below, a cyclic, unsaturated aldehyde might be expected to
form upon internal aldol condensation and dehydration of hexane
dialdehyde. Hexane dialdehyde is known to form upon ozonalysis of
cyclohexene .
'CHO CHO
H20
60
-------
SPECTRUM 1
SL
Oi
II
0>
"E
POSSIBLE STRUCTURES:
' CHO CHO
~ t. OR
0
0
"> r>.
CM o.
ll .. J.
CHO -
SO 60 70 90 3B 100 110 120 130 VtO ISO 5
M./ T,
SPECTRUM 2
"1-
CD_
r-
^"j
i^'-" -
,:..,
^
j
-------
Additional unsaturated aldehydes might be accounted for on the basis
(49)
of a reaction described by Cockcroft, et al. Upon photoisomer-
ization of 4,5-dihydroxyoxepin, the three products shown below were
obtained. Reported electron impact spectra of all three isomers
are similar to the helium chemical ionization spectrum for the
cyclohexene aerosol product.
o
CHO
CHO
4,5-DiHYDROXYOXEPIN
Consider now the spectrum in Figure 23, corresponding to chromatographic
peak 3. The methane spectrum is consistent with a molecular weight
of 112. Peaks are observed appropriate for protonated parent ion at
m/e 113, and adduct ions at m/e 141 and 153 (M + C2H5 and M + 03115).
The helium spectrum shows fragments at m/e 97, 69, and 43, consistent
with loss of CH-j, CH3-CO, and CH-j-CO-CO from the parent ion. A
possible structure consistent with the data is shown in the figure.
Finally, consider peak D, the mass spectrum for which is shown in
Figure 24. In the methane spectra, peaks consistent with protonated
parent and loss of water from protonated parent appear at m/e 99
and 81, respectively. In the helium spectrum, a peak at m/e 81 is
similarly observed, as is a peak at m/e 31, consistent with the
fragment CH2OH . The data suggest a primary alcohol of molecular
weight 98. Additional fragmentation is rationalized in the figure
and a possible structure is shown.
Structures presented in the last two figures suggest reactions of
greater complexity than those considered up to this point. Moreover,
62
-------
g SPECTRUM 1
8_
CO
POSSIBLE STRUCTURE:
0 0
ii n
CH3-CH=CH-C-C-CH3
t. Tn
in x
I CO
CO O
CO
r- m
*~ n
II Q>
50 60 TO 90 30 100 110 123 1JO 1W ISfl l«i !'
«y e:
SPECTRUM 2
''i.
CO
Ml
O
O
X
O
CO
n
CO
Oi
'
20 38 10 SO 60 TO 98 95 1W DO 12O I JO
FIGURE 23. ANALYSIS^OF CYCLOHEXENE AEROSOL, NEUTRAL FRACTION.
CHEMICAL IONIZATION MASS SPECTRA FOR CHROMATOGRAPHIC
PEAK B. SPECTRUM 1 BY METHANE CI-MS, SPECTRUM 2 BY
HELIUM CI-MS.
(Refer to Chromatogram in Figure 21)
63
-------
SPECTRUM 1
8~
0
0-
UlG
llT"
U.B
I*"
O. ~
CM-
ID
0
11
I
m
,?,
["""I1 '*r
POSSIBLE STRUCTURE:
HOCH2CH2CH=CH-CH=C
f
s
00
"E
ll nltllll , ttillt III ll I 'l!' I'ffr
20
-a so ee
30
SPECTRUM 2
B
OD.
a.
uc
CJbJ.
*
0:0
SS 60 70 98 38 108 118 128 130 ltt 158 168 1*70 IBB 138
FIGURE 24. ANALYSIS OF CYCLOHEXENE AEROSOL, NEUTRAL FRACTION.
CHEMICAL IONIZATION MASS SPECTRA FOR CHROMATOGRAPHIC
PEAK D. SPECTRUM 1 BY METHANE CI-MS. SPECTRUM 2 BY
HELIUM CI-MS.
(Refer to Chromatogram in Figure 21)
64
-------
retention of unsaturation may appear surprising in view of the
reaction conditions. It will be seen, however, that tentatively
identified products in cyclohexene and cv-pinene aerosols similarly
retain such unsaturation.
Cycloh_exe_ne Aerosol Basic Fraction
The quantity of basic matter obtained upon fracttonation of cyclo-
hexene aerosol was extremely limited (-0.2 mg) and was insufficient
for satisfactory analysis by GC-MS. Only in the case of a-pinene
aerosol was sufficient material obtained in the basic fraction to
permit such analysis. The general question concerning formation of
nitrogen-bases during aerosol reactions is considered in the section
dealing with the a-pinene aerosol.
ANALYSIS OF TOLUENE AEROSOL
Toluene Aerosol Acid Fraction
The water-insoluble acid fraction of toluene aerosol was isolated
as previously described, and was treated with diazomethane to yield
methyl esters and methyl-aryl ethers of the carboxylic acids and phenols.
The derivatized product was then analyzed by gas chromatography and
GC-MS. The reconstructed gas chromatogram is shown in Figure 25.
Structures have tentatively been assigned for five of the prominent
components and molecular weights have been assigned for two others.
It is notable that four of the molecular weights shown have odd values,
suggesting the presence of nitrogen.
The mass spectrum in Figure 26 corresponds to chromatographic peak B.
The prominent peak at m/e 159 corresponds to the protonated parent
ion. Strong adduct ions corresponding to (M + C2Hc ) and (M + £3115 )
are observed at m/e 187 and 199 respectively. This clearly establishes
the molecular weight as 158. Fragmentation corresponding to loss of
HCOOCH3 and loss of Cl^OH suggests the presence of carboxylic acid
methyl ester. Loss of CO suggests the presence of an aldehyde,
65
-------
CO
IBB 118 129 138 118 1SB 168 170 188 138 288 218 228 230 218 250 2GB 27B 288 230
FIGURE 25. ANALYSIS OF TOLUENE AEROSOL, ACID FRACTION METHYL ESTERS/ETHERS.
RECONSTRUCTED GAS CHROMATOGRAM FOR METHANE CI-MS.
-------
o
-o
6
JL
3
-Q
i £""*-«
I
O
i3_
;
i
1 13
k
*L
s_
D
*^~
~-
«3_
f*im fm^ M.JK M. _.
s
II
0)
E
ro
X
o
o
o
o
I
1
I
CM
ii
V
x"
O
«*
2 ^
ii *
5! 7
E o>
-£? 0 E
+' -1
2
\
( l'«'i"'i|""ii"V
\J
t- CM
E
X
E
fl.,....,f.t.,..f.r...(I.U
TENTATIVE ASSIGNMENT:
COOCH3
^C\
S CH CHO
*~
ii
fli /^ i i
^ Cri2
P x,^
CH2OH
X
f
r** o>
00 O)
1 II
ft} 4)
1 "E
in in
X X
o4 u
» *
,-! ,iii i ,/ *? i i
63 70 83 93 130 113 123 133 H3 153 163 173 183 133 233 210
FIGURE 26. ANALYSIS OF TOLUENE AEROSOL, ACID FRACTION METHYL ESTERS/ETHERS.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK B.
(Refer to Chromatogram in Figure 25.)
-------
and loss of H20 suggests the presence of alcohol. The structure shown
in the figure is consistent with such fragmentation and with the
molecular weight.
The mass spectrum in Figure 27 corresponds to chromatographic peak A.
The prominent peak for protonated parent ion at m/e 145 and the adduct
ions at m/e 173 and 185 indicate that the molecular weight is 144.
Observed fragmentation is analogous to the previous case. The
tentatively assigned structure is shown in the figure, and corresponds
to the next lower homologue of the product considered in the case
above.
The mass spectrum corresponding to chromatographic peak C is shown
in Figure 28. Peaks for the protonated parent ion and for the adduct
ions indicate that this product has a molecular weight of 167. Since
this is an odd number, the presence of nitrogen is indicated. Fragments
corresponding to loss of NO and N02 confirm this and indicate that
the product is probably a nitro compound. Fragmentation corresponding
to loss of CH^ may stem from the methyl ether group. Taking these
and other factors into account, the structure shown in the figure
is proposed. Substitution is not specified. It should be emphasized
that the original product would be a phenol. Treatment with diazo-
methane leads to the formation of the methyl ether.
The mass spectrum in Figure 29 corresponds to peak D in the reconstructed
gas chromatogram. Almost all of the comments concerning the last product
apply to the one considered here, with the exception that this spectrum
does not show a fragment corresponding to loss of NO. Nevertheless,
the evidence strongly suggests the proposed structure. Thus, it appears
that two isomeric nitro-cresols are formed. Since chromatographic
component D has a longer retention time than component C we can speculate
that substitution of component D renders it more polar than C. Some
possibilities are shown below.
68
-------
TENTATIVE
MORE POLAR
(GC PEAK D)
LESS POLAR
(GC PEAK C)
Consider next, the mass spectrum of chromatographic component E,
shown in Figure 30. The spectrum shows a strong protonated parent
ion and adduct ions indicating that the molecular weight is 183.
Again, the presence of nitrogen is indicated. There are peaks
consistent with loss of NO, N02, and H20. The strong peak for loss
of H20 is especially suggestive of an alcohol. Consistent with
these data the substituted benzyl alcohol is proposed.
The structures below summarize our findings to date concerning the
acid fraction of toluene aerosol. The formation of such homologous
degradation products parallels our findings concerning the aerosol
reactions of cyclohexene. In addition we see that both the methyl
group and the benzene ring of toluene appear to undergo attack in-
dependently. It is noteworthy that the most abundant components
of this fraction appear to be nitrogen-containing compounds and
that nitration of an aromatic ring appears to be taking place during
aerosol formation.
COOH
CH CHO
I
CH2
CH2OH
COOH
CH
CH2OH
CHO
CH3
NO 2
(TWO ISOMERS)
CH2OH
NO2
69
-------
B
-vj
o
B-
o
~
p_
1
D
>
!*-
8.
B.
D
*
*-
D ,
. ,,,..T
n
I
u
O
O
O
X
5
'"1"'
in
00
ii
0)
"E
i 1 ii
. .,,,,..,,,.I1, ,,.,.,,
f*.
r-
^
II
a
1
c
c
^
2
: ?
r
>" i
>
. 1
c
3
"i
^
f
Iflllllll
<>.
a
j
(N
:
c
»
I
il..|.m|
TENTATIVE ASSIGNMENT:
^ COOCH3
«- '
" ^ C NV
-| CH CHO
| CH2OH
y
^ ~
n »
a> -2?
^ +E
C ^
o °
i *
II
jy.l, ..^ jf.| ..11,...,^..! ...jf.-.l...
60 70 80 30 100 110 120 130 MO ISO 160 170 180 190
fl/ t
FIGURE 27. ANALYSIS OF TOLUENE AEROSOL, ACID FRACTION METHYL ESTERS/ETHER.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK A.
(Refer to Chromatogram in Figure 25)
-------
O
_
-
_
_
CM
IT)
S 3 Hv
11 ii ~E
| | *
E E i
* 0 V
Z Z I
i i s
1 1 1 II
ll -I.J.I ...l.llllllll [111, 1. II 111 1 .,1 1,1
TENTATIVE
ASSIGNMENT:
CH3
( ) -OCH3
N02
CO
to
II
I
(D
2
o
0) 1
+ " ^
ID
I-f
l^
-t- O
s --
, . ,,.1 .1 ,
j ,rn | r.,.|.tii tn.^in \.. t tin, j./.
60
7(5 8(5 30 190 110 120 130 110 ISO 160 173 I80 J90 2<5(5 210
M/ e
FIGURE 28. ANALYSIS OF TOLUENE AEROSOL, ACID FRACTION METHYL ESTERS/ETHERS.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK C.
(Refer to Chromatogram in Figure 25)
-------
(V
8
fc_
£*-
0.
$p_
*8
L"
£?_
8.
8_
o
.,,., J ,.l
1 1 j' !-- |
1
'
c
T
"
c
4
:
"f »""|"
\j
si
i
D
E
?
f
C
z
Ilk
1" ' ! '
' !
TENTATIVE
$ ASSIGNMENT:
1 C"3
X r/\,
+ /" X
i 1 (r7TN°2
OCH3
(O
2 00
^ o
II
-------
8
~J
(JO
8-
^
-
~~
_
-
-
1
, jfr
11 1 1 I III 1
MM, ijf, Il|if
Jill
ill!
T
''"
,1
i
i
1"
S
r~
ii
-₯
E_
o
z
X
1 1
*'
5
r
i
0)
T
g
<
+
^
X
«
^
,
s
11
-?
c
o
CM
X
"x
^
f
\ \ .,
Mil
1
!
1 liil
TENTATIVE
ASSIGNMENT:
CH2OH
t
/^
i
T
C 7T~ N°2
\^r
^xXx
" OCH3
r-
ii
-₯
E
"x
CM
f"
CM
II
0)
E
X
CM
O
-f
S
u lli.l Hill ii i>
190 200 ZlQ 220
60 70 80 90 100 110 120 ?36 JlO 150 JGO I7U
fl/ E
FIGURE 30. ANALYSIS OF TOLUENE AEROSOL, ACID FRACTION METHYL ESTERS/ETHERS.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK E.
(Refer to Chromatogram in Figure 25)
-------
Toluene Aerosol Neutral Fraction
The water-insoluble neutral fraction of toluene aerosol was isolated
as described previously, and was analyzed by gas chromatography and
GC-MS. The reconstructed gas chromatogram is shown in Figure 31,
Note that tentative assignments have been made for four major peaks
and molecular weights have been assigned to six others. In this
fraction one major and one minor peak have odd molecular weights,
suggesting the presence of nitrogen in these compounds.
The mass spectrum in Figure 32 corresponds to chromatographic peak B.
Peaks assigned to protonated parent ions and adduct ions suggest a
product of molecular weight 112. Loss of CH4 may arise possibly from
an intact methyl group, while loss of H-CO suggests the presence of
aldehyde. Consistent with these data a tentative structure is shown
in the figure.
The mass spectrum corresponding to chromatographic peak F is shown
in Figure 33. The spectrum is practically devoid of fragmentation,
but a strong protonated parent peak and reasonably prominent adduct
ions strongly suggest a molecular weight of 126. Very minor fragments
are evident which correspond to loss of l^O and CH^. This spectrum is
particularly ambiguous. A possible structure is shown in the figure.
The mass spectrum in Figure 34 corresponds to chromatographic peak A.
The spectrum is wholly devoid of significant fragmentation; peaks at
m/e 97 and 99 are considered spurious background in view of the
unrealistic M-12 and M-14 values. However, the molecular weight can
be determined with some confidence as 110 in view of the adduct ions for
(M + C2H5> and (M + 3115). The proposed structures shown in the figure,
however, are extremely resonance stabilized and could reasonably account
for resistance to fragmentation under conditions of chemical ionization
mass spec trome try (methane) .
74
-------
-------
ED
sr;
itj-
£
-------
-0
n.
CV.
O
O T-
II
O)
II
01
T O
i I
+ ro
I T.
Illlltll
a>
IT)
in
CM
liliii|iiii|iiM|lHt|...i|iiii[tiii)n.ni.4i
TENTATIVE ASSIGNMENT:
CH3
I
C
CH ^ ^CH2OH
CH
(O
CO
o
FIGURE 33. ANALYSIS OF TOLUENE AEROSOL, NEUTRAL FRACTION.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK F.
(Refer to Chromatogram in Figure 31)
-------
00
O
8_
IJ
Q_
LUO
U.G
UJ
o
0:0
0
CM
0
in
ii
SJ
E
CO
0
TENTATIVE
ASSIGNMENTS:
CH2
II
C
CH
CH
CHO
OR
CH
CHO
CHO
r-^
70 80 30 100 110 120 130 HO 150 160 170 180 1SG ZOO
«/ E
FIGURE 34. ANALYSIS OF TOLUENE AEROSOL, NEUTRAL FRACTION.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK F.
(Refer to Chromatogram in Figure 31)
-------
Finally, consider the mass spectrum in Figure 35, corresponding to
chromatographic component E. The spectrum is rather weak, but
significant adduct ions permit determination of the most probable
molecular weight as 116. The prominent peak corresponding to loss of
H20 strongly suggests the presence of alcohol functionality. Consistent
with these data, and with fragmentation of apparently related products
of toluene, a possible structure is shown in the figure.
The structures shown below summarize the finding to date concerning
the water-insoluble neutral fraction of toluene aerosol. As in the
previously considered product mixtures, we again observe sequential
oxidative degradation to give a series of related oxidation products.
CH-j
I CH3 CHO
CH CHO CH^ CHO CH^ "cH^H
CI~L CH5^ ^CH2OH
°h CH° CHO
| OR I CHO
CH^ CH. CHO
CHO pu-^x'
ANALYSIS OF q-PINENE AEROSOL
In studying the tf-pinene aerosol, extensive reference has been made
to the literature concerning reactions of this compound. This was
especially helpful during analyses of the neutral fraction, where
mass spectral data indicated the presence of many isomeric products.
Salient aspects of the literature survey are summarized under the
headings below. Detailed reviews of the chemistry of o/-pinene and
other terpines have been prepared by Simonsen and Templeton^
79
-------
00
o
g
O
Ui
<5
o>
ii
+
I
in
I
in
aa
~E
m
O
CH
CH2OH
TENTATIVE
ASSIGNMENT:
CHO
CH2OH
M.I|.|..|ltl||Mli
7CJ 80 30 100 110 123 1JO HQ 150 160 170 a;
M X* P
FIGURE 35. ANALYSIS OF TOLUENE AEROSOL, NEUTRAL FRACTION.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK E.
(Refer to Chromatogram in Figure 31)
-------
Qf-Pjnene Acid Fraction
The cy-pinene acid fraction was isolated as described previously, and
was treated with diazomethane to form methyl esters of the carboxylic
acids. The material was then analyzed by gas chromatography and
GC-MS. Figure 36 shows the reconstructed gas chromatogram. The
indicated chromatographic component whose mass spectrum is shown in
Figure 37 has been unequivocally identified as methyl-cis-pinonate by
comparison with an authentic sample of methyl-cis-pinonate. The mass
spectrum of the latter compound is shown in Figure 38. The mass spectral
fragmentation pattern for this compound is rationalized in Table 4-.
A second analysis of the sample by GC-MS verified the presence of
pinonic acid. The results indicated, in addition, that trans-pinonic
acid may be present along with the more abundant cis isomer. As
indicated below, interconversion of the isomers in the presence of
ultraviolet irradiation can be postulated. Tentative identification
of the chromatographic peaks corresponding to the isomeric pinonic
acid esters is indicated on the reconstructed gas chromatogram in
Figure 39.
COOH COOH
hv
H
CIS-PINONIC ACID ~ TRANS-PINONIC ACID
fl
-------
00
ID
METHYL PINONATE-
T
T
T
r
ae tew 110 120 13s
le ze 30 ie se so 70
SPECTPUM fOJ^GR
FIGURE 36. ANALYSIS OF a-PINENE AEROSOL, ACID FRACTION METHYL ESTERS.
RECONSTRUCTED GAS CHROMATOGRAM FOR METHANE CI-MS.
-------
> 90
80
<
_ 70 gj
W
_ 60 <
p
o
_ 50 ,
Ul
0
^
^»0 H
^
^
Ul
- 30 £j
_ 20
- 10
0
fi...,..-.f..l.l...-l ..1 |
i
i
j
- i
i
n
«.
i .1 It ii 1
i
a
r-
r-
T
1
-S
C
c
O5
(N
II
"E
j
i
Ui,....| lll]..l
ASSIGNMENT = Methyl Pinonate
0)
it
01 ^ a>
rn r**
₯ co E
II ^
Qi * +
"^ Q> 00 X
P *"" S
~E 1
10 SO 60 70 80 30 100 110 120 130 11O ISO 160 170 180 130 200
E
FIGURE 37. ANALYSIS OF a-PINENE AEROSOL, ACID FRACTION METHYL ESTERS.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE)
CORRESPONDING TO METHYL PINONATE.
(Refer to Chromatogram in Figure 36)
83
-------
100
CT>
_ 90 &>
n
03
_ so ~E
70 0.
UJ
CO
- 60 ^
u.
O
- 5C yj
0
- 40 ^
LU
U
' 30 DC
0.
. 20
- LO
1
j
II |]
CM
II
0>
E
^
--
ii
0)
E
AUTHENTIC
METHYL CIS-PINONATE
CH3
Kr--*o
X. COOCH3
T 1
v
\
\
X
O)
,
n
"E
Wr^llnJ...!
1
^
***^
0)
r^ r-
r II
II W
~E OT ^
7 +"
ii x
- I
,iil'M..I ill L. .11. nil
10 SO S3 70 80 90 100 110 120 130 110 ISO 16J 170 190 190 200
M/ E
FIGURE 38. CHEMICAL IONIZATION MASS SPECTRUM (METHANE) OF
AUTHENTIC METHYL CIS-PINONATE
84
-------
TABLE 4. RATIONALIZED FRAGMENTATION OF AUTHENTIC METHYL
PINONATE UNDER CONDITIONS OF CHEMICAL IONIZAT10N
MASS SPECTROMETRY (METHANE)
Process
Fragmentation of Parent-Ion
Fragment
Loss of H
Protonated parent-ion of
methyl pinonate,
+ m/e =
m/e
181
Loss of CH OH(MH -32)
Loss of HCOOCH.(MH -60)
Transannular cleavage
CH3-C' _ H
CH
3 H
0
CH3 H
CH
H
CH2
.C/-CHS
167
139
111
Iransannular cleavage
99
Transannular cleavage
II
CH3-C
H-^<3)
71
Transannular cleavage
CH
85
-------
Tentative identification of a secondary reaction product of Qf-pinene
has been made. The compound corresponds to peak A of the reconstructed
gas chromatogram in Figure 39. Its mass spectrum is shown in Figure
40. The compound is tentatively identified as the homologous acid
resulting from oxidative decarboxylation of pinonic acid, that is,
pinononic acid. Its mass spectral fragmentation pattern is rationalized
in Table 5. The compound is referred to as pinononic acid in accordance
(52)
with nomenclature of Simonson . In previous reports it has been
referred to using the derived name "nor-pinonic acid".
In summary the data indicate that under the simulated atmospheric
conditions a-pinene undergoes oxidative cleavage to pinonic acid.
The pinonic acid produced may then be oxidatively decarboxylated
(tentative) to the next lower homologous acid.
COOH
a-PINENE
PINONIC ACID
COOH
PINONONIC ACID
Formation of pinononic acid may also occur without intermediate for-
mation of pinonic acid. In a study of vapor-phase ozonation of
cv-pinene by Spencer, et al'5 ', an intermediate ozonide, C10H16°5>
was hydrolyzed to give pinononic acid directly. The authors speculate
that the intermediate was either verbenone oxoozonide or verbenone
peroxide ozonide
VERBENONE OXOOZONIDE
VERBENONE PEROXIDE OZONIDE
86
-------
00
-o
B
8_
PEAK TENTATIVE ASSIGNMENT
A pinonic acid, methyl ester
B cis-pinonic acid, methyl ester
C trans-pinonic acid, methyl ester
10 20 33 13 SO 0 70 60 30 100 110 120
SPECTRM NUTE8R
FIGURE 39. ANALYSIS OF a-PINENE AEROSOL, ACID FRACTION METHYL ESTERS.
RECONSTRUCTED GAS CHROMATOGRAM FOR METHANE CI-MS.
-------
g
00
oo
"
8_
8_
$P-
E
-
ft
n
68.
M
Co
3C
^ «
5
JR.
B.
D
"*
,-
ii
II
CD
1 E
1 1 Ii 1
10 160 170 180 130
FIGURE 40. ANALYSIS OF a-PINENE AEROSOL, ACID FRACTION METHYL ESTERS.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK A.
(Refer to Chromatogram in Figure 39)
-------
TABLE 5. RATIONALIZED FRAGMENTATION OF TENTATIVELY IDENTIFIED
METHYL PINONATE UNDER CONDITIONS OF CHEMICAL IONIZA-
TION MASS SPECTROMETRY (METHANE)
0
CH -C-w^ H bCH3 +
CH3 ,1 * (MH) , m/e = 185.
n +
Fragmentation of Parent-Ion
Process Fragment m/e
Loss of H 0(MH+-18) 167
0
+ CH,-cV H
Loss of CH3OH(MH -32) c.»\^~^» + 153
CH3 Cs°
0
Loss of HCOOCH (MH+-60) M^ ^~^^ 125
y?CH3
Transannular cleavage
CH,
^TH
+OH
CH,-C^ ^XCH3
Transannular cleavage > >ru_
H (3) 12) \^ f*»
Transannular cleavage J> <^ 71
Transannular cleavage ^"'^ _^ ^ 115
89
-------
In view of the identification of pinonic acid in model aerosol, this
compound was sought in rural air particulate matter collected^ in
the Blue Ridge Mountains. The sampling site was located in the
Pisgah National Forest, about 30 miles northeast of Ashville, North
Carolina. There was extensive conifer and hardwood forest cover.
The organic acid fraction of the air particulate matter was isolated
and treated with diazomethane, and the methyl esters were analyzed
by GC-MS. The reconstructed gas chromatogram is shown in Figure 41.
The mass spectrum shown in Figure 42 identifies the indicated
chromatographic peak as pinonic acid, by comparison with the mass
spectrum of an authentic sample (Figure 37).
The presence of pinonic acid was similarly sought in urban air
particulate collected in New York City (lower Manhattan). No
detectable concentration of the acid was observed.
Cf-Pinene Neutral Fraction
The water-insoluble neutral fraction of o-pinene aerosol products was
isolated as previously described, and was analyzed by gas chromatography
and GC-MS. The reconstructed gas chromatogram is shown in Figure 43.
Molecular weights tentatively determined from the mass spectra are
shown on the chromatogram. The data indicate that a number of isomeric
reaction products have been obtained. In order to aid identification
of these products various authentic terpenoids were obtained for use
as reference compounds. Selection of reference compounds was based
on a study of known reactions of a-pinene.
* Sampling and analysis of atmospheric particulate matter was conducted
under support of the previously cited program, "Haze Formation: Its
Nature and Origin"'3 '.
90
-------
100 110 120 130
0
10 20 30
SPECTRUM NUMBER
FIGURE 41 ANALYSIS OF BLUE RIDGE MOUNTAIN AEROSOL, ACID FRACTION METHYL ESTERS.
FIGURE 41. ANA QAS CHROMATOGRAM FOR METHANE C.-MS.
-------
5L
§_
^(0
"r-_J
tup
tQS-4
u,o
QLO_
O
n
OJ
60 70 80 30 100 110 120 139 110 ISO 160 173 180 190
MX E
FIGURE 42. ANALYSIS OF BLUE RIDGE MOUNTAIN AEROSOL, ACID FRACTION METHYL ESTERS. CHEMICAL
IONIZATION MASS SPECTRUM (METHANE) CORRESPONDING TO METHYL PINONATE
(Refer to Chromatogram in Figure 41)
-------
00
CD
H
"go 60 TO «j' 30 100 VlO 'iffl 'l30 1« ISO 'lW 'l 'lW 30D 3l° 3ZD
FIGURE 43. ANALYSIS OF a-PINENE AEROSOL, NEUTRAL FRACTION.
RECONSTRUCTED GAS CHROMATOGRAM FOR METHANE CI-MS.
-------
(54)
Studies Based on Known Reactions of
-------
(47)
A study by Mayer, et al , indicates that when Q"-pinene is simply
irradiated using a Pyrex filter, several products are obtained (low
yields). One of the most abundant is d-limonene. Limonene itself
can react in the presence of nitrogen oxides, or by "autooxidation"
to form carveol.
CH,
HO
AUTOOXIDATION
OR NOx + 02
a-PINENE
CHj- *-uri2
LIMONENE
CARVEOL
Jefford reports that reaction of photogenerated singlet oxygen with
tt-pinene results in greater than 99 percent yield of ^rans-3-hydroperoxv-
pin-2(10)-ene.
OOH
'-PINENE
TRANS-3-HYDROPEROXY-PIN-2(ini-FNF
A reaction of this type could presumably occur in aerosol containing
a suitable sensitizer. The hydroperoxide may undergo unimolecular
or bimolecular reaction to yield the hydroxy or carbonyl compounds,
pinocarveol and pinocarvone. (Although neither pinocarveol nor
pinocarvone could be obtained for use as reference standards, note
that "in the chromatogram, Figure 43, two peaks have molecular weights
corresponding to that of pinocarveol, 152'.
95
-------
PtNOCARVEOL
(59)
PINOCARVONE
Dupont and Zacharowitz ^ showed that oxidation of Q'-pinene in the
presence of selenium dioxide yields myrtenol and myrtenal. This
is significant with respect to atmospheric chemistry because both
selenium dioxide and singlet oxygen lead to allylic oxidation. Both
compounds below were obtained for use as reference standards.
CH2OH
Se02
CHO
MYRTENOL
MYRTENAL
(60)
Henderson and Sutherland "' observed that hydrogen peroxide treat-
ment of Q'-pinene in acetic acid yields principally limonene, a-terpineol,
borneol, and p-methane-1>4,8-triol.
H,0;
2^2
ACETIC
ACID
CH
3 OH
or-PINENE
LIMONENE a-TERPINEOL BORNEOL
p-MENTHANE-
1,4,8-TRIOL
Although the above is a liquid-phase reaction in acetic acid, it
should be pointed out that hydrogen peroxide has been observed in
the atmosphere and in model systems^b1^. it was observed in irradi-
ated mixtures of hydrocarbon/NOx and in the urban atmosphere during
periods of photochemical smog formation.
96
-------
Finally, oxidation of cv-pinene by perbenzoic acid has been described.
(62)
The reaction is of interest in that perbenzoic acid oxidation might
be expected to yield products similar to those formed in the presence
of peroxyacyl nitrates. The perbenzoic acid oxidation was shown to
yield pinene oxide. Treatment of pinene oxide with water at 115-112 C
yields pinol. Hydration in the presence of dilute acid leads to ring
fission and formation of sobrerol.
PERBENZOIC
ACID
a-PINENE
i-PINENE OXIDE
PINOL
CH3-
SOBREROL
Of the cy-pinene reaction products described above, those listed below
were obtained for use as reference standards. Commercial samples
of sobrerol, pinol, and pinene oxide could not be obtained.
(1) d-limonene
(2) terpinolene
(3) fenchyl alcohol
(4) fenchone
(5) 1-borneol
(6) Q'-terpineol
(7) cis-terpin (hydrate)
(8) trans-verbenol
(9) 1-carveol
(10) myrtenol
(11) myrtenal
Mixtures of these authentic compounds were analyzed by GS-MS. The
reconstructed gas chromatograms are shown in Figure 44. Mass spectra
are shown in Figures 45-50. In the paragraphs below, the comparison
standards have been grouped by molecular weight, and a-pinene neutral
products of appropriate molecular weight are compared in turn with the
reference spectra. A reconstructed gas chromatogram showing the
97
-------
B
8
JS-
ls_
B_
o
1C 2C 30
SPeCTHLM NLKER
60 78 BO
'108 110 '128 '130 '110 '.SO 160 170 'iBC 'l9B
8.
8-
o
o
|iiii|ini|Mi.,
90 100 110 120 130 1KJ ISO 160 170 l» Jae
FIGURE 44. RECONSTRUCTED GAS CHROMATOGRAMS OF AUTHENTIC
TERPENOIDS.
98
-------
8
#-*
RJ
R,
,, ...,.,
1,1
.j.....,,... p...(..,,. j. J.f ,).-. ,JTrrf fj...f1., 471-11 jfTJ r.f in 4 j
60 73 90 a? I« 110 120 130 IV IbO JKQ 17(3 J8Q
R.
8.
C:
R.
D
TERPINOLENE
CH3
6B 7(5 89 30
n/E
)l(J 120 130 |« ISfl 16«
FIGURE 45. CHEMICAL IOIMIZATION MASS SPECTRA (METHANE) OF
AUTHENTIC LIMONENE AND TERPINOLENE.
(Refer to Chromatograms in Figure 44)
99
-------
B
R_
8.
8.
R_
a-FENCHYL ALCOHOL
1 1 ' ' 1 "yT""i""i"-j"-r]r
so 79 w ap in? no 120 iap
"?,--|
fl ISO 160
B_
BORNEOL
I
i 1 i I i I
68 70 60 » 1 HP IIP 120 130 ! VH ISO )60
n/E
FIGURE 46. CHEMICAL IONIZATION MASS SPECTRA (METHANE) OF
AUTHENTIC a-FENCHYL ALCOHOL AND BORNEOL.
{Refer to Chromatograms in Figure 44)
100
-------
B
8_
hR_
5«
Rj
Ju
...M....1~..T~TTrnT.'"]-<
60 70 W 3
rt/E
a-TERPINOL
llL
i'Vi-(""'""V ' !
11(3 123 !30 1KJ Iti3 16? 173 Iflfl
R_
B_
S.
R_
MYRTENAL
CHO
Jl
r--T-j-»-n
""'""I .....
eo 19 eo am jw 11? 12? lad
n/e
ISP i«i !?a :«a
FIGURE 47. CHEMICAL IONIZATION MASS SPECTRA (METHANE) OF
AUTHENTIC a-TERPINOL AND MYRTENAL.
(Refer to Chromatograms in Figure 44)
101
-------
8_
F-
S_
60
JW 110 )2(7
H2O
(C1QH2O O2 'H2O)
TERPIN HYDRATE
I
)50 16(3
fl/E
8
PI
8.
!«.
R.
D
CH.
O
FENCHONE
1 !""'""l I I I""!"11]
GO 70 X X IflB 110 120 130 110 ISO 160
FIGURE 48. CHEMICAL IONIZATION MASS SPECTRA (METHANE) OF
AUTHENTIC TERPIN HYDRATE AND FECHONE.
(Refer to Chromatograms in Figure 44)
102
-------
g
8.
8_
MP
08-
WL
w
^ yi
fit ^3
jT
R-
o
,111 II. LUl 1
CH3
f^M
\[x^ OH
trans-VERBENOL
I
1
In
1,1,1 1 Illu !ll,M , III All . il
*5 50 SO 70
nx e
30 I W 110 520 130 110 ISO 160
R.
S.
B.
BJ
D
ee TO ee x loo no 120 130 110
M/E
FIGURE 49. CHEMICAL IONIZATION MASS SPECTRA (METHANE) OF
AUTHENTIC trans-VERBENOL.
(Refer to Chromatograms in Figure 44)
103
-------
I
R.
8.
P-
I*.
8.
B.
CARVEOL
60 70 80 30 100 tl8 120 130 110 ISO 160
S.
F-
8_
1*.
CH2OH
MYRTENOL
Lf
ILL
L L
i ,....,.-.--,-...,-..,- ,-.-,.., r...,j»ttj
60 70 80 30 100 118 12C 13B 110
n/r
FIGURE 50. CHEMICAL IONIZATION MASS SPECTRA (METHANE) OF
MYRTENOL AND CARVEOL.
(Refer to Chromatograms in Figure 44)
104
-------
tentatively assigned molecular weights of the aerosol products was
shown in Figure 43. Surprisingly, these comparisons did not produce
any satisfactory spectral matches.
Borneol, cc-fenchyl alcohol, and a-terpineol have molecular weight 154;
their mass spectra are shown in Figures 46 and 47. Compare with these
spectra that for chromatographic peak E shown in Figure 51 (the chroma-
togram is shown in Figure 43). In view of the lack of definitive frag-
mentation, no structure has been assigned to this aerosol product.
Nevertheless, peaks at m/e 155, 183, and 195 are characteristic of a
compound of molecular weight 154. A weak peak at m/e 137 is consistent
with loss of H20 and suggests the possibility that the product is an
alcohol. However, the base peak of the compound is clearly at m/e 109.
This fragment is rather small in each of the standard spectra. More-
over, the standard spectra show characteristic fragments at m/e 81 and
95; these fragments are absent in the product spectrum. Thus, it is
highly unlikely that the product corresponds to any of the above three
standards.
The mass spectrum shown in Figure 52 has been tentatively identified as
pinononic aldehyde, as shown. (The spectrum will be discussed in
detail, below.) There is no evidence to suggest that it corresponds to
any of the above standards.
Verbenol, myrtenol, carveol, and fenchone have molecular weight 152;
their spectra are shown in Figures 48-50. Compare to these spectra
that for chromatographic Peak B (from Figure 43) as shown in Figure 53.
Although this spectrum is weak, peaks at m/e 153 MH ) and 135
(MH+ - H20) suggest the possibility of an alcohol of molecular weight
152. The product exhibits some fragmentation characteristics" of all
the above standard alcohols, but is most similar to verbenol. (Figure
49; note duplicate analyses of the standard.) However, in comparing
the product spectrum to that of verbenol note that the peaks at m/e 101
105
-------
g
R.
S_
g^_
Q-
&EL
CUE)
6
prF)
Q_°°~
R..
E3
EJ
1 (III 111 i I
...... ,, i, .,..-,,.. im- M..n( ,-.,,- r
C8H13+
1
ii
V
E
^
in
in -~
r- ^ ^-
II + +
a 5
^ + +
^ ^
-H2O (?) =
!l f I 1. i r , j j j| i i 1 Ii tiii mi
Ml >|i I....... w .1....I.- ij ,i , ,.,,,.. , ., I ... ti M . I , . .. . : . | . ( I I . . . | .11 . I . . . M . . 1 I 1 .. I M "> '
70 80 9? 100 110 12(3 130
ISO 160 170 180 190 200
FIGURE 51. ANALYSIS OF a PINENE AEROSOL, NEUTRAL FRACTION.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK E.
(Refer to Chromatogram in Figure 43)
-------
E>
TENTATIVE ASSIGNMENT:
CH3
ro
ii
U4
o
+
i
ib
f
U)
in
n
Q)
~E
.,
rtH
.,.
.,.
.,.
160 170 190
FIGURE 52.
60 73 80 90 100 110 120 130 1 H3 ISO
U/ E
ANALYSIS OF a-PINENE AEROSOL, NEUTRAL FRACTION.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK C.
(Refer to Chromatogram in Figure 43)
-------
o
GO
§
8.
CL
UJE;
tote.
EJ
FIGURE 53.
70 90 00 100 110 125 130 1«5 ISC 160 170
M/ E
ANALYSIS OF a-PINENE AEROSOL, NEUTRAL FRACTION.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK B.
(Refer to Chromatogram in Figure 43)
-------
and 93 exhibit reversed intensity. Thus, assignment of the product as
verbenol would be rather speculative.
The mass spectrum of chromatographic Peak A (from Figure 43) is shown
in Figure 54. The spectrum is rather ambiguous and does not permit
assignment of a structure; the molecular weight may be 152. Observed
fragmentation is entirely inconsistent with the above reference
compounds.
Myrtenal was a molecular weight of 150. Limonene and terpinoline have
molecular weight 136. Their mass spectra are shown in Figures 45 and
47. The mass spectra for the a-pinene neutral fraction did not indi-
cate the presence of any components with these molecular weights.
In concluding this discussion, it should be emphasized that mass
spectral fragmentation patterns observed for various terpenoids have
tended to be somewhat variable from one analysis to the next. Frag-
mentation of these compounds is especially sensitive to instrument
variability. This can be seen in spectra for trans-verbenol obtained
upon duplicate analyses (Figure 49). In the illustrated case, the
analyses were made about 1 year apart during different research
programs. During the current work,analyses of standards and unknowns
were performed over a period of several days, and reanalysis of
standards was conducted. Nevertheless, in analysis of these sensitive
compounds, there is a possibility that slight instrument variabilities
may be significant. Thus, it is not possible to completely rule out
the presence of the reference compounds in the reaction mixture. Re-
analysis of materials in hand with special attention to instrument
conditions should help to eliminate the present ambiguity concerning
this phase of the study.
Tentative Assignments for q-Pinene Neutral Products--Although the
above studies of authentic compounds have not led to unambiguous
109
-------
8.
ip-
I8~
bB_
If Ft
is
8_
EJ
o>
n
1
£
n
1
60 70 80 90
.1.1 .
1=
~
CO
in
n
"l
M IIQ 12Z 133 110 ISO ISO 170 180 190
M/ E
FIGURE 54. ANALYSIS OF a-PINENE AEROSOL, NEUTRAL FRACTION.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK A.
(Refer to Chromatogram in Figure
-------
identification of a-pinene reaction products, tentative assignments for
various products are considered in this section. Some are based upon
comparison of the sample fragmentation pattern with that observed for
authentic methyl pinonate. An especially helpful diagnostic has been
the fragmentation arising from (proposed) transannular cleavages. In
examining the mass spectra shown in Figures 52 and 55-58 below, it may
be helpful to refer to Table 4 (p.85 ) in which the fragmentation of
authentic methyl pinonate is rationalized.
As a point of departure, it would be reasonable to expect formation of
pinonic aldehyde, as shown below. Formation of this compound would be
analogous to formation of pinonic acid as observed in the acid fraction.
CH3 CH3
>0CHO
Pinonic aldehyde has a molecular weight of 168. As indicated in
Figure 43, six components of the neutral fraction have been tentatively
assigned molecular weights of this value. Fragmentation patterns of
these components have not permitted unambiguous assignment of the
proposed structure to any of the six candidate products. Nevertheless,
there is a strong likelihood that this compound is indeed involved in
the aerosol reactions of a~pinene.
Consider the mass spectrum in Figure 52. This corresponds to Peak C
in the reconstructed gas chromatogram Figure 43. The compound is
tentatively identified as pinononic aldehyde. Fragmentation appears
to be analogous to that of authentic methyl pinonate. Key fragments
are rationalized in the figure. This product might arise from oxida-
tive degradation of the homologous dicarbonyl, as indicated below. Its
formation might be considered analogous to formation of pinononic acid,
observed in the acid fraction.
11 1
-------
ACID
FRACTION
COOH
PINONIC ACID
CHO
PINONONIC ACID
NEUTRAL
FRACTION
COOH
PINONIC ALDEHYDE PINONONIC ALDEHYDE
(POSTULATED)
Consider next, the mass spectrum shown in Figure 55. This corresponds
to Peak F in the reconstructed gas cLi.omatogram. The tentatively
assigned structure is shown. As in the previous case, the fragmentation
is rationalized in the figure, and appears to be analogous to that of
methyl pinonate.
Finally, consider the mass spectrum shown in Figure 56. This corre-
sponds to Peak G in the reconstructed gas chromatogram (Figure 43).
Again, the tentative assignment is based on comparison of the indicated
fragments to those of authentic methyl pinonate.
In view of the last three proposed assignments, it is not unreasonable
to present the scheme shown below. This scheme is not meant to
suggest mechanistic considerations, but is clearly a possible route for
the formation of a series of sequentially degraded oxidation products.
112
-------
Formation of the proposed products shown above involve, in each case,
cleavage of the carbon-carbon double bond. Studies cited earlier
indicated that cc-pinene can undergo "autooxidation" in the presence of
air, moisture, and sunlight to yield sobrerol (see p. 93). Formation
of this product involves cleavage of the cyclobutane ring with reten-
tion of an intact carbon-carbon double bond. If the cyclobutane ring
were cleaved at the alternative internal position, an isomeric diol
might additionally be formed, as shown in the structures below. Further
oxidation or oxidation/dehydration might be expected to yield the
compounds shown below.
113
-------
~
Set
y j _
§
gp-
0-
ftg
&
U.ED
QLO_
(f PD
fr ^"^^
^p
ft\
f*j
g«-
E3
N_
r>
m
D
Q
-V
* /
o
i
X
o
II
1 1
c_>
X*
1
""'""1
eo *:
CO
^
^
'**"
tl
1
^ 5
V-
3
c
I
c
1
<_
z
{.
II
1
c
3
1,
K3
t
»
i
5
5
g oo
/i
i 1 1
ii,.. i. i i
93
O)
01
II
-SJ
^
CO CO
I I
0 U
M
s\
Xs ^.
o-° I
+ n
I
CJ
'
t.. .1. I, ...I.I. II 1 1 1
joe no 120
TENTATIVE ASSIGNMENT:
CH3
J^
^^ 0
*C CHO
^^S.^
CHOH
\J/
^_
^
to
V T-
"^
c 11
i i
O -in
oo O £
X CN "
o
+ J. «
i x ^
X
Lm, ,,,,L,; i, ., ,
........... .,..,. i i i < i ' i i
1 "3fi 1 ^K3 1 ^0 1 60 1 7? 1 9C 1 H
M/ E
FIGURE 55. ANALYSIS OF a-PIIMENE AEROSOL, NEUTRAL FRACTION.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK F.
(Refer to Chromatogram in Figure 43)
-------
nr>_
a.
u.o
o
F)
CL
X X
+ V° T
1 *
.£? CO M
£ z x
0 0 u
\/
II
o>
°*0A
CO
X
O
3
II
^
CO
t
1!
_»
'r
CH3 CH3
Jl CH TENTATIVE ASSIGNMENT:
^"^sX^
CH3
-------
a-PlNENE
SOBREROL,
POSTULATED
OH
POSTULATED
CO]
CH3 CH
CHO
Mass spectra tentatively identified as consistent with these structures
are shown in Figures 57 (hydroxycarvotanacetone) and 58, Peaks D and H
in Figure 43. Rationalization of fragmentation is presented in the
figures. Spectral interpretation in these cases, would be greatly
aided by availability of a spectrum of authentic sobrerol for com-
parison. As mentioned previously, no commercial sample of this com-
pound could be obtained. It is noteworthy, however, that in these
last two spectra, the diagnostic fragments associated with the presence
of an intact cyclobutane ring (i.e., transannular cleavage fragments
at m/e 71 and 99; see Tables 4 and 5) are absent or very weak.
Thus, we suggest that under simulated atmospheric conditions, a-pinene
reactions include cleavage of the cyclobutane ring, and that such
cleavage may occur with retention of the carbon-carbon double bond.
a-Pinene Basic Fraction
Of the model aerosol systems studied, only in the case of a-pinene was
there sufficient material obtained to permit analysis of the basic
fraction (see Table 3 p. 29 ). Although the basic fraction was negli-
gibly small in all cases, analysis of the basic fraction for at least
116
-------
E
R.
0-
t^JEO
r?
U.E)
SL
UJ
(/)
CO
<
m/e = 109
<
UJ
O)
O
CM
I
m/e = 151
en
*T
rf
TENTATIVE ASSIGNMENT:
CH3
CH3-C-CH3
I
OH
o
"-
it
O)
O)
-»-
I
o
!.), ,,.!,.
-.,,
I
'1
60 73 03 90 100 110 120 130 1-W 150 163 170 180 190 200 210 220
E
FIGURE 57. ANALYSIS OF a-PINENE AEROSOL, NEUTRAL FRACTION.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK D.
(Refer to Chromatogram in Figure 43)
-------
oo
R.
8.
o
o
CM
+
I
(D-
60
FIGURE
70
MX
58.
so
10J
TENTATIVE ASSIGNMENT:
CH3 CH3
-"""" . 'C<^o
8 cH3 y
7 ^H2
«J +
E m/e = 111
O
I
O in
5 £
* c*
I 1 Jl
^^^^^^^^^"1 " * «-§' ' """
1lfl 12B 133
in «
CH3 CH3
1 VJ
Nj^ Ch
\/
II
O
5
)
to
O «o «~
0 - ii
n
+ -S
X -5! i
S E
+
^
' T.
: ^
u
0
o x -£
CM S fc
X
"L.
1 1 1
1 . 11 il il 1 i 1 i
110 195 16G 170 If
.
if)
X
CM
U
s
IL l lllinVl I 1 "mil
J«3 J90 209 213
CO
CM
CM
II
4J
^
in
X
CO
O
5
22CJ 230
ANALYSIS OF a-PINENE AEROSOL, NEUTRAL FRACTION.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK H.
(Refer to Chromatogram in Figure 43)
-------
one aerosol was desirable to determine if any nitrogen bases were
indeed formed under atmospheric simulation.
Analysis of the a.-pinene basic fraction by GC-MS did not suggest the
presence of any nitrogen bases, nor-indeed, the presence of any nitrogen
containing products. The spectra obtained are in fact typical of those
observed for the a-pinene neutral fraction. That is, the "basic"
fraction appears to be composed primarily of neutral reaction products.
This can be explained by reference to the fractionation procedure.
As described previously, a methylene chloride solution of the water-
insoluble aerosol products was extracted with dilute aqueous sodium
hydroxide and with dilute hydrochloric acid. The basic fraction was
defined as that material extracted into the dilute acid. During the
acid extraction, a small quantity of (insoluble) neutral material was
apparently entrained or emulsified in the dilute acid wash, and was
thereby carried along with the "basic" fraction. In future work, this
will be avoided by carefully backwashing the dilute acid phase with
solvent before the aqueous phase is made alkaline and extracted with
solvent. An analogous backwashing procedure will be used in the isola-
tion of the acid fraction. In summary, it appears that if any genu-
inely basic products are formed, their concentration is vanishingly
small in the material analyzed.
Several representative mass spectra obtained for this fraction are
presented in order to illustrate the "neutral" character of the com-
ponents. The reconstructed gas chromatogram is shown in Figure 59.
Consider the mass spectrum shown in Figure 60, corresponding to chroma-
tographic Peak A. The spectrum is extremely similar to that observed
for the neutral product considered earlier in Figure 52. A fragment
consistent with the protonated parent ion is observed at m/e 155 and
peaks consistent with loss of carbon monoxide and water are observed
at m/e 127 and 137 respectively. Key fragments consistent with
119
-------
N3
O
SPECTHJt
3*
aw
«a
130
iw
9» sia
s*
FIGURE 59. ANALYSIS OF a-PINENE AEROSOL, BASIC FRACTION.
RECONSTRUCTED GAS CHROMATOGRAM FOR METHANE CI-MS.
-------
8
CO CO
~
cn_
g_
a.
If"
bED
LO-
t-W
3
IB"
0
C\J_
ED
°-
X
X
o
CO
o
I
*
II
~E
X
1
X
i^M
in
00
n
-SJ
E
°,x A
1
CO CO "" N, ' NT
IX I
CJ O *
V
^ I
0 X C,H3
( 1
" ^^"^n
o <^
§ L
n ^X. ^.CHO
_» r»-
E o "-
0 " TENTATIVE ASSIGNMENT
Ql
1 * I
ii + "
i +
^ s i
iff<>pHllllii|iiil[iiti|l»Hiiii|iMi|iiiniiii|iiiiiiiii[inifi'"f""l"l-j -i----!" i-
53 63 78 80 93 103 113 120 133 1« ISO 360 \TO 180 133
FIGURE 60. ANALYSIS OF a-PINENE AEROSOL, BASIC FRACTION.
CHEMICAL 10NIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK A.
(Refer to Chromatogram in Figure 59}
-------
transantiular cleavage are observed at m/e 71, 85, and 99. Thus, the
product is tentatively assigned the structure shown, identical to that
proposed in Figure 52 .
Consider the mass spectra shown in Figure 61; they correspond to chroma-
tographic Peak B. The upper spectrum was obtained using methane as
the chemical-ionization reagent gas. The lower spectrum was obtained
using helium as the reagent gas; hence it is much like an electron-
impact spectrum. The methane spectrum is consistent with a molecular
weight of 138, although the satelite peak at (M + 29) is very weak.
Using the Battelle peak-matching program, the helium spectrum was com-
pared with a computerized file of 11,000 electron-impact spectra. The
sample spectrum corresponded very closely with that of terpinoline.
Consistent with this finding and with the apparent molecular weight
determined from the methane spectrum, the product is tentatively
assigned as terpinoline.
Finally, consider the spectrum shown in Figure 62 corresponding to
chromatographic Peak C. The structure shown in the figure is especially
tentative. The peak assigned as the protonated parent ion is consistent
with a molecular weight of 182. Fragments consistent with loss of H20
and loss of CH2=C=0 plus H20 are observed. Peaks diagnostic of an
intact cyclobutane ring are absent. Consistent with these data, a
speculative structure is shown.
The above described spectra are typical of those observed for the
"basic" fraction. The results suggest that this fraction consists
principally of a small quantity of neutral product carried over during
an incomplete fractionation step.
122
-------
- SPECTRUM 1
SL
?>
iSj
I
Si.i_
E_
..lil.i
j|
i. ILL
O)
«
1,
ill..
*~
II
1
X
. - -
o>
CM
+
~l
TENTATIVE
ASSIGNMENT
(see text)
A
O
CH X
TERPINOLENE
SO «>fl 7ff 10 i«P 13P
HX f
FIGURE 61. ANALYSIS OF a-PINENE AEROSOL, BASIC FRACTION.
CHEMICAL IONIZATION MASS SPECTRA FOR CHROMATOGRAPHIC PEAK B.
SPECTRUM 1 BY METHANE CI-MS, SPECTRUM 2 BY HELIUM CI-MS.
(Refer to Chromatogram in Figure 59)
123
-------
IX)
8«
00-
JED
U.D
ID
~
-
............111,..
..1.
1
1
T"
1
1
1
, iji
o
CM
I
0
II
11 fM
o> X
> O
1
I
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M/ E
FIGURE 62. ANALYSIS OF a-PIIMENE AEROSOL, BASIC FRACTION.
CHEMICAL IONIZATION MASS SPECTRUM (METHANE) FOR CHROMATOGRAPHIC PEAK C.
(Refer to Chromatogram in Figure 59)
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SECTION V
REFERENCES
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August 1973.
(2) Air Pollution Control District, Los Angeles County, "Effectiveness
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Project, Final Report, 1966.
(3) Altshuller, A. P., Bufalini, J. J.t Environ. Sci. Technol., 5, 39
(1971).
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(1965).
(5) Altshuller, A. P., Cohen, R. R., presented at American Chemical
Society Meeting, Division of Water, Air, and Waste Chemistry,
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(9) Endow, N., Doyle, G. S., Jones J. L. , ibid, 13, 141 (1963).
(10) Goetz, A., Pueschel, R. F., Atmos. Environ.T 1, 287 (1967).
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4-9, 1965b.
(14) Hayakawa, I., J. Air Pollut. Contr. Assoc., 14, 339 (1964).
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-------
(16) Orr, C., Jr., Hurd, F. K., Corbett, W. J., J. Colloid Sci., 13.
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Waste Chemistry, Atlantic City, N. J., Sept. 13-17, 1962.
(20) Schuck, E. A., Ford, H. W., and Stephens, E. R., "Air Pollution
Effects of Irradiated Automobile Exhaust as Related to Fuel
Composition", Air Pollution Foundation Report 26, October, 1958.
(21) Stephens, Edgar R., Price, Monty A., Atmos. Environ. 3, 573 (1969).
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Press, New York, New York, 1968.
(22) Stevenson, H.J.R., Sanderson, D. E., Altshuller, A. P., Int. J. Air
Water Pollut., 9, 367 (1965).
(23) Titnmons, R. G. , presented at General Motors Research Laboratories
Symposium on Chemical Reactions in Urban Atmospheres, GMC, Warren,
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(24) Wayne, L. G., and Romanovsky, J, C., "Rates of Reaction of the Oxides
of Nitrogen in Photo-oxidation of Diluted Automobile Exhaust Gases",
Chemical Reactions in the Lower and Upper Atmosphere, Interscience,
New York, 1961, p. 71.
(25) Wilson, Wm. E., Jr., Merryman, E. L., Levy, A., J. Air Pollut. Cont.
Assoc.. 21, 3 (1971).
(26) Wilson, Wm. E., Jr., Miller, D. F., Trayser, D. F., and Levy, A.,
"A Study of Motor Fuel Composition Effects on Aerosol Formation.
Part III Visibility Reduction from Automobile Exhaust". Battelle,
Columbus Laboratories Report to the American Petroleum Institute
Committee for Air and Water Conservation (February 1972).
(27) Wilson, Wm. E. , Jr., Levy, A., "A Study of Sulfur Dioxide in
Photochemical Smog", American Petroleum Institute, Project S-ll,
Battelle, Columb'us Laboratories, Columbus, Ohio, 1968.
126
-------
(28) Miller, D. FCJ Levy, A., and Wilson, Wm. E., Jr., "A Study of Motor
Fuel Composition Effects on Aerosol Formation. Part II, Aerosol
Reactivity Study of Hydrocarbons", Battelle, Columbus Laboratories
Report to the American Petroleum Institute Committee for Air and
Water Conservation (February 21, 1972).
(29) Levy, A. and Miller, S. E., "Final Technical Report on the Role of
Solvents in Photochemical Smog Formation", to National Paint, Varnish,
and Lacquer Association, Battelle, Columbus Laboratories,Columbus,
Ohio, 1970.
(30) Landstrom, D. K. and Kohler, D., "Electron Microprobe Analysis of
Atmospheric Aerosols", to National Air Pollution Control Administration
(CPA-22-69-33) (1969).
(31) Henry, W. M. and Blosser, E. R., "A Study of the Nature of the
Chemical Characteristics of Particulate Collected from Ambient Air",
to National Air Pollution Control Administration (CPA-22-69-153)
(1970).
(32) Schuetzle D. , Cuttenden, A. L., and Charlson, R. J., "Application of
Computer Controlled High-Resolution Map Spectrometry to the
Analysis of Air Pollutants", J. Air Poll. Control Assoc., 23 (1970).
(33) Schwartz, W. E., Jones, P. W., Riggle, C. J., and Killer, D. F.,
"The Organic Composition of Model Aerosols", invited paper presented
at the Eastern Analytical Symposium, New York, New York, November
1973.
(34) Wilson, Wm. E., Jr., Schwartz, W. E., and Kinzer, G. W., "Haze
Formation -- Its Nature and Origin", a Battelle-Columbus Report to
the Environmental Protection Agency (CPA 70-Neg. 172) and The
Coordinating Research Council (CAPA 6-68) January 1972. Reference
is made to results of research conducted during the contract period
June 1972 - June 1973 and presented in the first annual report.
(35) Wilson, W. E., Jr., Miller, D. F., Levy, A., and Stone, R. K., "The
Effect of Fuel Composition on Atmospheric Aerosol Due to Auto
Exhaust", J. Air Poll. Control Assoc..23. 949 (November 1973).
(36) Lonneman, W. A., Kopczynski, S. L., Darley, P. E., and
Sutterfield, F. D., "Hydrocarbon Composition of Urban Air
Pollution", Environ. Sci and Techno^., 8. 229 (March 1974).
(37) Kopczynski, S. L., Lonneman, W. A., Sutterfield, F. D., and Darley,
P. E., "Photochemistry of Atmospheric Samples in Los Angeles",
Environ. Sci. and Technol_.,6, 342 (April 1972).
127
-------
(38) Rasmussen, R. A., J. Air Poll. Control Assoc.. 22, 537 (1972).
(39) Rasmussen, R. A., Proc. Nat. Acad. Sci.,53, 215 (1965).
(40) Fieser, L. F., J. Amer Chem. Soc., 76 1945 (1954).
(41) Fieser, L. P., J. Amer Chem Soc., 75 4386 (1953).
(42) Seeback, D., Jones, N. R., and Corey, E. J., J. Org. Chem.,33,
300 (1968).
(43) Handbook of Silylation, Pierce Chemical Company, P. 0. Box 117,
Rockford, Illinois 61105, 1972, pp. 19-20.
(44) Corey, E. J., J. Org. Chem.,32, 4160 (1967).
(45) Brown, R., Adv. Org. Chem., 3 89 (1963).
(46) Miller, D. F., Schwartz, W. E., Jones. P. W., Joseph, D. W. ,
Spicer, C. W. , Riggle, C. J., and Levy, A., "Haze Formation: Its
Nature and Origin", second annual report of the U. S. Environmental
Protection Agency and the Coordinating Research Council, submitted
by Battelle, Columbus Laboratories, June 1973.
(47) Mayer, R., Bochow, K., and Zieger, W., Z. Chem.4, 348 (1964).
(48) Jones, P. W., and Adelman, A. H., "A Novel Preparation of Cyclic
Sulfites throug1 'tosulfoxidation of Alkenes", Tetraheldron, 30.
2053, (1974).
(49) Cockcroft, R. D., Waali, E. E., and Rhodes, S. J. Tetrahed. Lett..
41, 3539 (197(n.
(50) Simonsen, J. L., "The Terpenes", Vols. I and II, Cambridge University
Press, London, c. 1953.
(51) Templeton, W., "An Introduction, to the Chemistry of Terpenoids and
Steroids", Butterworth and Company, Ltd., London, c. 1969.
(52) Simonsen, J. L., op. cit., Vol II, p. 140.
(53) Spencer, C. C., Weaver, W. I., Oberright, E. A., Sykes, H. J.,
Burney, A. L., and Elder, A. L., J. Qrg. Ghem.,610, 5 (1940).
(54) Simonsen, J. L., op. cit. Vol. II, pp. 136-139.
(55) Templeton, W., op. cit. p. 62.
128
-------
(56) Banthorpe, D. V., and Whittaker, D., q. Rev. Chem Soc.,20,373
(1966).
(57) Ternpleton, W. op. cit. pp 67-68.
(58) Simonsen, J. L., op. cit. Vol I, p. 300 and p. 166.
(59) Dupont, G., and Zacharowitz, W., and R. Deilou, Compt. Rend., 198,
1699 (1934).
(60) Henderson, G. G. , and Sutherland, M. M. , J. Chem. Soc., 101 2288
(1912).
(61) Gay, B. W. , and Bufalini, "Hydrogen Peroxide in the Urban
Atmosphere", paper presented at the 161st American Chemical Society
National Meeting, Los Angeles, March 1971.
(62) Simonsen, J. L. , op. cit., Vol II p. 141.
129
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TECHNICAL REPORT DATA
fl'leasc read Instructions on llic /ri'mr hi'fori' completing}
1 . REPORT NO.
EPA-650/3-74-011
4. TITLE AND SUBTITLE
Chemical Characterization
2.
of Model Aerosols
7. AUTHOFKS)
Warren E. Schwartz, Peter W. Jones,
Charles J. Riggle, and David F. Miller
9. PERFORMING ORG '\NIZATION NAME AND ADDRESS
Battelle
' Columbus Laboratories
505 King Avenue
Columbus, Ohio 43201
12. SPONSORING AGENCY NAME AMP ADDRESS
Chemistry (, Physics Laboratory
National Environmental Research Center
Environmental Protection Agency
Research Triangle Park, N. C. 27711
IS. SUPPLEMENTARY NOTES
3. RECIPIENT'S ACCESSIOWNO.
5. REPORT DATE
August 1974
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO
1O. PROGRAM ELEMENT NO. ~
1AA008
1 1. CONTRACT/GRANT NO.
801174
13. TYPE OF REPORT AND PERIOD COVE RET
Final: 6/72-6/74
14. SPONSORING AGENCY CODE
16. ABSTRACT '
Model aerosols were generated fro-n individual hydrocarbon precursors and nitrogen
oxides under simulated atmospheric conditions in a 17.3 m environmental chamber.
Hydrocarbon precursors employed were toluene, alpha-pinene , and cyclohexene.
Aerosols were collected on glass-fiber filters and organic matter was obtained
by solvent extraction. Organic reaction products were fractionated into acid
neutral, and basic components, and were analyzed in detail by techniques
including gas chromatography and gas chromatography combined with mass spectro-
metry. The study also included evaluation of techniques for selective
derivatization of aerosol products.
A variety of polyf unct ional reaction products were identified, including alcohols
aldehydes, ketones, carboxylic acids, and phenols. Tentative identification of
nitrogen containing products was also accomplished, including nitrate esters
and aromatic nitro compounds.
This report was submitted in fulfillment of Grant Number R-801174 by the Columbus
Laboratories of Battelle Memorial Institute under the sponsorship of the
Environmental Protection Agency. Work was completed as of April 30, 1974.
17.
a. DESCRIPTORS
Aerosols
Smog
Air Pollution
Chemical Analysis
Gas Chromatography
Mass Spectrometry
Environment Simulation
Environment Simulators
13, DISTRI BUTI ON STATEMENT
Release Unlimited
KEY WORDS AND DOCUMENT ANALYSIS
b. OENTIFI E RS/OPEN ENDED TERMS
Model Aerosols
Organic Aerosols
Aerosol Chemistry
Atmospheric Chemistry
Organic Chemical
Analysis
Smog Chamber
19. SECURITY CLASS (This Report/
Unclassified
20. SECURITY CLASS (Tliis pan?)
c. COSATI I iL-IU/<;roup
04 -A
07-C
07-E
21 NO. OF PAGES
129
22. PRICE
EPA Form 2220-1 (9-73)
130
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