The beta-Silicon Effect in the Solvolysis of the Carbocation System Destabilized by alpha-CF3

Abstract

Solvolysis rates of 1-trifluoromethyl-1-(X-substitutedphenyl)-2-(dimethylphenylsilyl)ethyl esters were determined conductimetrically in 60% (v/v) aqueous ethanol. The effects of aryl substituents on the solvolysis rate at 25°C were correlated with Yukawa-Tsuno Eq. against σ parameter of r=1.25 which is characterization of β-silylated α-CF₃ cation system. This r value is identical to the value with α-H (r=-3.07). The results suggest that the silyl participation mechanism should remain the same in both α-CF₃ and α-H systems.