Solvent effects on the reduction mechanism of 9-chloroanthracene, 3-nitrobenzyl chloride and 3-chloroacetophenone

The reduction mechanism of 9-chloroanthracene, 3-nitrobenzyl chloride and 3-chloroacetophenone has been investigated in detail by means of cyclic voltammetry and controlled potential bulk electrolysis. The investigation was carried out in a number of aprotic solvents in order to elucidate the importance of solvation phenomena on the various parameters associated with the reaction mechanism, i.e., cleavage, hydrogen abstraction, protonation and dimerization rate constants as well as standard potentials. In this connection, the influence of the supporting electrolyte in terms of ion pairing and double layer effects has been considered. For the radical anions of 9-chloroanthracene and 3-nitrobenzyl chloride the logarithm of the cleavage rate constant shows a linear dependence on the Gutmann acceptor number and donor number, respectively, whereas no clearcut correlation can be observed in the case of the radical anion of 3-chloroacetophenone. The rate constant obtained for the protonation reaction between 3-nitrobenzyl anion and 3-nitrobenzyl chloride is to an even higher extent influenced by the nature of the solvent. The trends in the solvent effects are discussed.