Solvent Effect on the Rate of β-Scission of the tert-Butoxyl Radical

The transient absorption spectrum of the tert -butoxyl radical in the UV region was obtained by the laser flash photolysis technique. The rate constants for β-scission and self-termination reactions of tert -butoxyl radicals were measured in five solvents; the Arrhenius parameters of the rate constant for β-scission k β were determined. It was shown that both the solvent polarity and ability for hydrogen bonding accelerate the reaction of β-scission. The solvent effect on the rate constant of the β-scission reaction is discussed in terms of a simple Onzager−Betcher model, a point dipole model, and a model of the H-bonded complex of the radical with the solvent molecule.