V-/EPA
United States
Environmental Protection
Agency
Environmental Sciences Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S2-80-204 Feb. 1981
Project Summary
Polynuclear Aromatic
Compounds
Synthesis and Purification
E.J. Eisenbraun
This report reviews and discusses
the synthesis and/or purification of
polynuclear aromatic (PNA) com-
pounds commonly found as pollutants
in the environment. It also presents
details of the experimental procedures
and techniques as well as the chromo-
tographic and spectroscopic evidence
of structure and priority of the com-
pounds supplied to the U.S. Environ-
mental Protection Agency. In addi-
tion, it describes the apparatus
designed and constructed to meet the
synthesis needs together with safety
improvements for handling toxic
compounds.
Introduction
The final report upon which this
summary is based (see box at end of
paper for ordering instructions) provides
details of synthesis and purification of
10-g samples of 10 hydrocarbons, 6
nitrogen heterocyclics and 2 oxygen
heterocyclics for use as instrumental
standards and in other studies at the
Chemistry and Physics Laboratory of the
EPA's North Carolina Environmental
Research Center. The compunds are
listed in alphabetical order for each
category in Table 1
Compounds Obtained Through
Purification of Available
Materials
Purification Techniques
Since several of the compunds
needed by EPA were commercially
available (3,6,11,12,13,14, and 16), and
purification rather than synthesis was
indicated, it became important to
examine and utilize any and all
purification routes.
An earlier report (EPA-600/2-78-
006) described techniques and
apparatuses which became important
in laboratory practices for safe
production of the final pure compounds.
Because some of the products and
intermediates were suspected
carcinogens, final handling procedures
were reviewed. Included were
development of an improved Soxhlet
apparatus, a modified sublimation
apparatus, a solid sample dispenser and
apparatus for safe cleaning of
laboratory equipment. Zone refinement
was also used for purification and the
refinement apparatus was redesigned
to improve refinement methods.
The improved Soxhlet and
sublimation apparatuses became
important for achievement of "project
goals in'this study; they should prove
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Table 1. Compounds Supplied to
the EPA during the
Reporting Period
Hydrocarbons
Benzo[ghi]perylene (1), mp 276-277°C,
J0.4g
Benzo[e]pyrene (2), mp 178-179 °C,
9.96 g
Chrysene (3f. mp 251-253 °C, 11.6g
Coronene (4). mp 437-440 °C, 10.5 g
1,2,3,6,7,8-Hexahydropyrene (5)a'h, mp
133-134°C, W.Og
sym-Octahydroanthracene (6)&'h, mp
72-73 °C, 13.7 g
Perylene (7), mp 275-277 °C, 13.2 g
1,2,3,4-Tetrahydroanthracene W'b, mp
89-90 °C, 10.3 g
4,5,9,10-Tetrahydropyrene (9)a'ti, mp
139-140 °C, 10.4 g
1,10-Trimethylenephenanthrene (10),
mp 80.5-81.0 °C, 13.2 g
Nitrogen Heterocyclics
Acridine (11 )a, mp 109-110 °C, 12.7g
Benzo[f]quinoline (12)", mp 90-91 °C,
12.9 g
Benzo[h]quinoline (13)*, mp 50.5-
51.5°C, 11.1 g
Carbazole (14)**, mp 243-244 °C,
10.5 g
11H-lndeno[1,2-b]-quinoline (15), mp
167-169 °C, 10.7g
Phenanthridine (16)*, mp 106.5-
107.5 °C, 12.1 g
Oxygen Heterocyclics
Dinaphtho[2,1 -b: 1', 2'-d]furan (17), mp
156-157 °C, 10.7g
peri-Xanthenozanthene (18), mp
241-242 °C, 9.7g
^Compound available from commercial
source and not synthesized.
^Compound resulted from shared cost
and effort.
equally useful to other researchers.
Design details are shown below
(Figures A-1 and A-2 from the final
report).
Generally, the individual samples
were contained in about 100 vials and
ranged from 9.9 to 13.7g. The
redesigned sampling device greatly
aided the safe handling of toxic
compounds.
Analytical and preparative high-
pressure liquid chromatography which
became available during EPA support of
this project were valuable for
determining purity of samples. A
description of the technique used in
purifying a sample of sym-octahydro-
anthracene is described in the final
report.
Nitrogen heterocyclic PNA com-
pounds were purified using one or more
of the techniques listed above. Attempts
to purify acridine (11) failed until
complexation with catechol proved
successful. Since acridine (11) was one
of the later compounds used, no
experience was available to indicate
whether its usage would be practical
with other nitrogen heterocyclics.
Compounds Synthesized
The compounds shown in Table 1,
excluding the seven exceptions, were
synthesized. In each case, the final
report provides the synthesis route and
experimental details.
Coronene (4) is difficult to synthesize
on an increased scale because starting
55/50
Sintered
Glass —
Plate
Teflon
Stopcork
h
^ Glass Seal
0 1 2
4O 1 1 1
Scale-Inches
material at an advanced stage on
synthesis is scarce; also, the higher
temperatures required, especially in the
sublimation of 4 and its intermediates,
adds to the difficulty.
A heater, which operates at 500+ °C,
was developed. This heater is essential
to the scale-up preparation of 1,4, and 7.
An improvement in preparation of
perylene and development of an
alternate route which does not require
perylene were major factors in the
synthesis scheme.
The following reactions provided an
increased yield of 1 and eliminated a
step in the synthesis of coronene (4).
Preparation of 24 (scheme 1 of the final
report) is shown by the following partial
scheme.
Selective reduction through catalytic
hydrogenation, dissolving metal
reactions, and HI-P4 reductions proved
to be important in the synthesis of
several PNA compounds (2,8,9,10). The
direct conversion of 1 -tetralone to
napthalene by heating in the presence
of a mixture of NaOH-KOH has been
extended to the preparation of 1,2,3,4-
tetrahydroanthracene (8) as shown in
the final report (scheme 3).
This reaction shows promise for th
synthesis of specific hydroaromatics.
Figure A-1.
An improved soxhlet
apparatus.
Figure A-2.
An improved sublima-
tion apparatus.
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24
"Maleic anhydride, A. "Pc/CA. cCuz,
quinoline, A.
KOH-NaOH, A
compounds are an integral part of
petroleum, petroleum products, coal
liquids, and shale oil. While there is a
current diminished interest in the
synthesis of pure aromatic compounds
in air pollution studies, other
environmental problems requiring high
purity standards which involve PNA
compounds are bound to emerge as the
uses of coal and petroleum products,
which are rich in polynuclear aromatics
and their hydrogenetive derivatives,
continue to increase.
Recommendations
In an earlier report (EPA-600/2-78-
006) the use of staple isotopes as labels
was suggested in PNA aromatics. Their
partially hydrogenated derivatives will
become more important and systematic
synthesis of representative labelled
compounds should be initiated. The
pure standard samples (labelled and
unlabelled) would then be available as
advances in instrumentation and
pressures for controlling pollution
occur. Large-scale synthesis of 13C
labelled compounds is a reality; for
example, in another project, this
laboratory produced 100g samples of
two different aromatic hydrocarbons
containing a single specific 13C label
with a 95% + 13C.
Given the rapidly escalating costs of
synthesis, some attention should be
directed to consolidating inter- and
intra-governmental agencies to support
future synthesis projects.
contrast, very selective hydrogenation
conditions are required to produce 8
from anthracene.
Instrumental Studies
Gas liquid chromatography and high-
pressure liquid chromatography were
used to determine priority of the
intermediate and final PNA compounds.
The identity of each was established
through the synthesis route and use of
spectroscopy studies (IR, UV, 'HNMR,
and 13CNMR) as well as mass
spectrometry. From these data, HNMR
was the most definitive. With the
exception of coronene (mass spectrum
supplied as substitute), a photoreduced
1HNMR trace was included in the final
report.
Conclusions
The synthesis and chemistry of PNA
compounds are of interest to a broad
spectrum of industrial and govern-
mental laboratories because these
E.J. Eisenbraun is with the Oklahoma State University. Department of
Chemistry, Stillwater, OK 74078.
Jamas £.Meeker is the EPA Project Officer (see below).
The complete report, entitled "Polynuclear Aromatic Compounds—Synthesis
and Purification." (Order No. PB 81-125015; Cost: $9.50, subject to change)
will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
> U.S. GOVERNMENT PRINTING OFFICE. 1M1 -757-012/7008
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