No abstract

Can. J. Chem. 70, 121 (1992). The electrochemical oxidation and reduction potentials of a number of substituted 1-methylnaphthalenes (la-1) and 1-naphthylmethyl radicals (2a-1') as well as 2-methylnaphthalene (3) and the 2-naphthylmethyl radical (4') have been measured by cyclic voltammetry and photomodulation voltammetry. The oxidation potentials correlate with a+ (p+ = -7.1 and -8.4 for 1 and 2' respectively) while the reduction potentials correlate with a (p-= 10.1 and 13.0 for 1 and 2' respectively). The relative magnitude of the p values can be rationalized when the charge density distribution in these systems is considered. This leads to the interesting conclusion that even though a full charge is placed in the IT-system of 1 when it is oxidized or reduced, the fraction of the charge that accumulates at C, is actually less than in 2+ or 2-where only 50-70% of the charge is delocalized into the ring. A correlation between p for the redox reactions of 1 , 2', benzyl, diphenylmethyl, and cumyl and the calculated (AMI) charge density at C, is established, implying that the sensitivity of the corresponding ions to substituent effects increases as the fraction of charge at that site increases. The redox data have been used in thermochemical cycles in order to estimate the substituent effect on the homolytic, mesolytic, and heterolytic cleavage reactions of 1 and its corresponding radical ions. The implication of these results on the C-C cleavage versus deprotonation of radical cations and on the photochemical homolysis versus heterolysis of naphthylmethyl halides and-acetates is discussed.

ChemInform Abstract The electrochemical oxidation and reduction potentials of substituted benzyl, cumyl, and diphenylmethyl radicals such as (I)-(III) are found to give linear correlations with σ+ and σ-, resp., (solvent effects, relationship between the redox potentials and the charge separation in the transition state for solvolysis).