Absolute Rate Expressions for the Abstraction of Hydrogen by Primary, Secondary, and Tertiary Alkyl Radicals from Thiophenol

Article abstract of DOI:10.1021/ja00183a040

Absolute rate expressions for the abstraction of hydrogen from thiophenol in nonane by tert-butyl, isopropyl, n-butyl, and n-octyl radicals were determined by kinetic absorption spectroscopy (KAS).Alkyl radicals were produced by photolysis of dialkyl disulfides or by photolysis of mixtures of di-tert-butyl peroxide and trialkylphosphine in the presence of thiophenol.Arrhenium expressions for alkyl radicals from the phosphine method from 255 to 355 K were as follows: n-butyl, log(k/M^-1s^-1)=(9.40+/-0.13)-(1.74+/-0.21)/θ, θ=2.303RT kcal/mol; isopropyl, log(k/M^-1s^-1)= (9.26+/-0.19)-(1.70+/-0.21)/θ; tert-butyl, log(k/M^-1s^-1)=(9.26+/-0.26)-(1.50+/-0.20)/θ.Rate constants at 298 K vary from 0.8E8 to 1.5E8 M^-1s^-1 for hydrogen-transfer reactions.