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. (C) 1998 John Wiley & Sons, Ltd.
|Autori:||Bellucci G; Chiappe C|
|Titolo:||Radical bromination of 1,1- and 1,2-diphenylethylenes in 1,2-dichloroethane|
|Anno del prodotto:||1998|
|Digital Object Identifier (DOI):||10.1002/(SICI)1099-1395(1998100)11:10<685::AID-POC17>3.0.CO;2-C|
|Appare nelle tipologie:||1.1 Articolo in rivista|