The leaving group dependence in the rates of solvolysis of 1,2-diphenylethyl system

Detailed Analysis for the Solvolysis of Isopropenyl Chloroformate

The specific rates of solvolysis (including those obtained from the literature) of isopropenyl chloroformate (1) are analyzed using the extended Grunwald-Winstein equation, involving the N(T) scale of solvent nucleophilicity (S-methyldibenzothiophenium ion) combined with a Y(Cl) scale based on 1-adamantyl chloride solvolysis. A similarity model approach, using phenyl chloroformate solvolyses for comparison, indicated a dominant bimolecular carbonyl-addition mechanism for the solvolyses of 1 in all solvents except 97% 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). An extensive evaluation of the outcomes acquired through the application of the extended Grunwald-Winstein equation resulted in the proposal of an addition-elimination mechanism dominating in most of the solvents, but in 97-70% HFIP, and 97% 2,2,2-trifluoroethanol (TFE), it is proposed that a superimposed unimolecular (S(N)1) type ionization is making a significant contribution.