2,2,2-Tri(aryl and alkyl)ethyl Xanthatesの熱分解反応

抄録

Pyrolysis of 2, 2, 2-tri (aryl and alkyl) ethyl S-methyl xanthates (RCH₂OCSSCH₃) afforded olefins accompanying 1, 2-shift of the aryl group. To elucidate this reaction mechanism, kinetic studies were made. The first-order rate constants for pyrolysis of xanthates in a variety of solvents were determined. Judging from the solvent effect estimated on the basis of E_T-value, the solvent effect on the reaction rate of VIII (R=CH₃-(C₆H₅)₂C) and IX (R=C₆H₅(CH₃)₂C) appears too small to attribute the reaction mechanism to the one via an ion pair which has been already proposed. However, in the case of V (R=(C₆H₅)₃C), the solvent effect, Hammatt parameter, ρ=+1.35, and also kinetic isotope effect, k_H/k_D=1.21, indicate that the reaction may have an ionic character.