Kinetic Isotope Effects in Electron-Transfer Reactions

1 Kinetic Isotope Effects in Electron-Transfer Reactions 

Deuterium substitution rednces the electron affinity of organic snbstrates. The reduced electron affinity of deuterinm-snbstitnted analogs is due to the larger electron-donating effect of deuterium when compared to hydrogen. Its inductive constant is small bnt negative (-0.0011). The deuterium electron donor effect develops in organic ion-radicals also. 

The formation of N,iV -dialkyl-4,4 -bipyridine cation-radical proceeds through the reduction of the corresponding dication (alkylviologen) by tributylphosphine. Yasui et al. (2001) measured the reaction kinetics in the acetonitrile-methanol mixture. The rate of cation-radical formation decreases in all of the cases when the alkyl groups are deuterated. 

Dimethylsulfide accelerates the decomposition of tert-bntylperoxybenzoate (Pryor and Hendrickson 1983). Dimethylsulhde acts as a donor, whereas the peroxide acts as an acceptor. Strictly nnder the same conditions, the rate of the peroxide dissociation in the presence of Me2S is almost 1.5 times greater than that in the presence of ( 03)28 (Pryor and Hendrickson 1983). 

For the reactions of MeLi with benzophenone and the benzophenone that was labeled at the carbon atom of the carbonyl group, ratio is 1.000 in ether at 0°C. Under the same conditions, this ratio is 1.023 for MeLi addition to the carbonyl pair of 2,4,6-trimethylbenzophenones 

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