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New Hydrogen Transfer Catalysts
Author(s) -
Morgenthaler Jens,
Rüchardt Christoph
Publication year - 1999
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/(sici)1099-0690(199909)1999:9<2219::aid-ejoc2219>3.0.co;2-d
Subject(s) - chemistry , anthracene , photochemistry , pyrene , kinetic isotope effect , radical , hydrogen atom , substituent , catalysis , solvent , acceptor , electron transfer , medicinal chemistry , organic chemistry , deuterium , physics , alkyl , quantum mechanics , condensed matter physics
The transfer of hydrogen from excess 9,10‐dihydroanthracene (DHA) to acceptors such as α‐methylstyrene is catalyzed, i.e. occurs at temperatures in the range 200–260 °C instead of 280–320 °C, when hydrocarbons with weaker C–H bonds than DHA, e.g. 6 H ‐benzo[ cd ]pyrene ( 4 ), 7 H ‐dibenzo[ a,kl ]anthracene ( 5 ), 4‐methyl‐7 H ‐benzo[ de ]naphthacene ( 6 ) or 8 H ‐dibenzo[ b,fg ]pyrene ( 7 ), are added to the reaction mixture. The reactions are initiated by bimolecular H‐atom transfer from 4 – 7 to the acceptor (retrodisproportionation) and proceed by nonchain radical mechanisms. This is supported by isotopic labelling and kinetic isotope effects, substituent and solvent effects, EPR spectroscopy of intermediate radicals, and by a comparison of the thermochemical and kinetic characteristics of these reactions.