United States
                Environmental Protection
                Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
                Research and Development
EPA/600/SR-98/124    September 1998
EPA       Project  Summary
                Substitution  Reactions for the
                Detoxification of  Hazardous
                Chemicals
                Fred K. Kawahara
                  Recent literature on  substituting
                chemical reagents that will convert toxic
                halogenes to their nontoxic hydrocar-
                bons was surveyed. Within this cat-
                egory of chemical substitution, three
                types of reactions are discussed:  su-
                peroxide ion radical reactions, polyeth-
                ylene glycol (PEG) transformations of
                PCBs, and catalytic hydrogen transfer
                reactions.
                  This Project Summary was developed
                by EPA's National Risk Management
                Research Laboratory, Cincinnati, OH,
                to announce key findings of the re-
                search project that is fully documented
                in a separate report of the same title
                (see  Project Report ordering  informa-
                tion at back).

                Background
                  Chemical substitution is one of several
                techniques available to treat hazardous
                chemicals that can threaten the environ-
                ment. In  the report, briefly summarized
                here,  chemical treatment is substituting
                hydrogens for halogens so as to convert
                the halogenated organics to hydrocarbons
                or to  mineralize  the organic to carbon
                dioxide, water, or other components).
                  Three types of reactions applicable to
                the conversion of hazardous chlorohy-
                drocarbons to their respective  nontoxic
                hydrocarbons are discussed:
                  • superoxide ion radical reactions,
  • dehalogenation of polyhaloaromatics
   and polyhaloalkanes with PEGs; and
  • catalytic hydrogen transfer reactions.

  Some fundamental aspects of these re-
actions are reported.
  With O2 representing molecular oxygen,
a one-electron reduction in  its  valence
yields the ion radical O2 —. Studies are
cited  that demonstrate reactions caused
by this superoxide ion radical, e.g., PCS
oxygenation.
  Use of PEG, together with a base such
as potassium  hydroxide, has been found
to be a promising technique. On reporting
on processes involving PEG'S use, how
PEG  functions as the reactive agent to
dechlorinate PCB is developed.
  With the catalytic transfer hydrogena-
tion reactions, organic acceptor molecules
are catalytically reduced with hydrogen
donated by another organic molecule. The
literature review of catalytic transfer hy-
drogenation is restricted to certain  reac-
tion conditions and solvent effects and to
some details in molecular donor and ac-
ceptor structures.  Studies on the effects
of temperature, solvents, solvents in het-
erogeneous systems, homogeneous ca-
talysis, and heterogeneous  catalysis  on
transfer reductions are included.
  The full report is a valuable survey of
recent literature (incorporating almost 100
citations) on this subject; it is not intended
as a manual on technical application.
                                                                 Printed on Recycled Paper

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The EPA author, Fred K. Kawahara, is with the National Risk Management
  Research Laboratory, Cincinnati, OH 45268.
The complete report, entitled "Substitution Reactions for the Detoxification of
    Hazardous Chemicals," (Order No. PB98-177876; Cost: $25.50, subject to
    change) will be available only from:
       National Technical Information Service
       5285 Port Royal Road
       Springfield, VA 22161
        Telephone: 703-605-6000
The EPA author can be contacted at:
        National Risk Management Research Laboratory
        U.S. Environmental Protection Agency
        Cincinnati, OH 45268
   United States
   Environmental Protection Agency
   Center for Environmental Research Information
   Cincinnati, OH 45268

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