Critical Evaluation of Studies Employing Alkenyl Halide 'Mechanistic Probe' as Indicators of Single Electron Transfer Processes

摘要

Recently it has been suggested that many reaction traditionally classed in polar terms may proceed via single electron transfer (SET) processes. The results of experiments with rearrangeable alkenyl halide probes have often been cited as evidence to support the conclusion that an SET mechanism is operative. Serious complications in this analysis have surfaced. This Account critically evaluates the utility of these alkenyl halide probes as mechanistic probes for SET. Reactions which interfere with the standard analysis include the rearrangement of non-radical intermediates and the isomerization of the starting probe halide by a halogen atom transfer mechanism. Guidelines are presented which are useful in evaluating the accuracy of past conclusions drawn from alkenyl halide probe experiments and in designing future experiments which are free from complication. Keywords: Electron transfer, Mechanistic probes, Free radicals, Kinetics.