Kinetics and mechanism of the reaction of substituted benzyl bromides with copper in dimethylformamide

The reaction of copper metal with various substituted benzyl bromides in dimethylformamide has been studied and the kinetic and thermodynamic parameters of the reaction have been obtained. Hammett plots of log(k/k degrees) vs the substituent constant sigma gave good correlations (rho = 0.24, S-rho = 0.03, r = 0.951). The structure of the organic group has little effect on the rate of reaction of substituted benzyl bromides with copper. In the absence of atmospheric oxygen, oxidative dissolution of copper occurred by the mechanism of single-electron transfer with the formation of 1,2-diphenylethanes and copper(I) complexes. The stereochemistry and intermediate compound were also studied and the reaction mechanism is discussed. Copyright (c) 2005 John Wiley & Sons, Ltd.