Electron-transfer reactions. Systems: dimeric dicarbanions of α-methylstyrene + pyrene or + perylene

Abstract

Reactions of pyrene (π) and perylene (Pe) with dimeric dicarbanions of α-methylstyrene (^–αα^–) were investigated in tetrahydrofuran at 25°C. The reaction of pyrene proceeds according to the following mechanism: [graphic omitted] followed by fast reaction of [graphic omitted] with ^–α. or π. The following values were obtained: K_π= 120 M, k₁= 1.3.10^–2 sec^–1, k₂K₁∼1.5 × 10^–5 M sec^–1, and k₂/k_–1= 8.5 × 10^–2 M.

The direct endothermic electron-transfer ^–αα^–+π→^–αα. +π^–. (1′) is much slower than the formation of the adduct ^–ααπ^–. Its decomposition supplies ^–αα. more rapidly than reaction (1′). The exothermic electron-transfer [graphic omitted] is probably faster than the addition [graphic omitted]. Thus, the kinetics of the stationary state provides k₂/k_–1=(k_–1+k′_–1) and k₂K₁(K₁=k₁/(k_–1+k′_–1).

The reaction of perylene is too fast to be followed by our techniques, but electron-transfer from ^–αα^– to [graphic omitted] was investigated. The following mechanism was established: [graphic omitted] The product k₂[graphic omitted] is 6.5 × 10^–2 sec^–1.