KINETIC-STUDIES OF THE HOMOGENEOUS COUPLING REACTION BETWEEN ELECTROCHEMICALLY GENERATED AROMATIC RADICAL-ANIONS AND ALKYL RADICALS

Radicals produced via the indirect reduction of alkyl halides by aroma tic radical anions are likely to couple fast with the mediator. In the presence of activated olefins or good hydrogen atom donors the fate o f the alkyl radicals might be changed. In this study rate constants fo r the coupling reaction (2) between primary, secondary and tertiary al kyl radicals and some aromatic radical anions were measured via the co mpetition with addition of the radical to styrene or ethyl cinnamate, or via the competition with hydrogen atom transfer from thiophenol or 2-methyl-2-propanethiol to the alkyl radical. It is shown that for all the alkyl radicals and aromatic radical anions investigated so far th e rate constant for coupling is close to 1 x 10(9) M-1 s(-1).