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Radical bromination of 1,1‐ and 1,2‐diphenylethylenes in 1,2‐dichloroethane
Author(s) -
Bellucci Giuseppe,
Chiappe Cinzia
Publication year - 1998
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/(sici)1099-1395(1998100)11:10<685::aid-poc17>3.0.co;2-c
Subject(s) - halogenation , chemistry , medicinal chemistry , kinetic isotope effect , trifluoromethyl , product distribution , reagent , dichloroethane , organic chemistry , solvent , catalysis , deuterium , physics , alkyl , quantum mechanics
The radical bromination of 1,1‐ and 1,2‐diphenylethylenes in 1,2‐dichloroethane was investigated on the basis of kinetic and product distribution data. Whereas the ionic process followed a third‐order rate law (second order in Br 2 ), the radical bromination was second order in Br 2 and zero order in olefin in the reagent concentration range examined. Significant inverse kinetic isotope effects were found for the bromination of 3,4′‐bis(trifluoromethyl)‐1,1‐diphenylethylene and cis ‐1,2‐diphenylethylene under these conditions. At variance with the ionic bromination, which gave mixtures of meso ‐ and d , l ‐dibromides only the meso ‐dibromides were obtained both from the cis ‐ and trans ‐1,2‐diphenylethylenes. The kinetic and product distribution data for the radical process are discussed in terms of a mechanism in which caged radical intermediates are formed. © 1998 John Wiley & Sons, Ltd.