Mechanistic Studies of the Reactions of Silicon−Carbon Double Bonds. Addition of Alcohols to 1,1-Diphenylsilene

Abstract

The addition of water, aliphatic alcohols, and acetic acid to 1,1-diphenylsilene (generated by photolysis of 1,1-diphenylsilacyclobutane) has been studied in polar solvents using steady-state and nanosecond laser flash photolysis techniques. Absolute rate constants and (selected) deuterium kinetic isotope effects for the addition of water, methanol, ethanol, 2-propanol, tert-butyl alcohol, and acetic acid have been determined at 23 °C in acetonitrile solution. Silene quenching follows a linear dependence on quencher concentration over the range investigated in all cases and proceeds with rate constants which vary over a range 4.1 × 108−1.6 × 109 M-1 s-1. The rate constants exhibit small primary deuterium kinetic isotope effects in all cases except acetic acid. Rate constants for addition of methanol, tert-butyl alcohol, and acetic acid have also been determined in hexane and THF solution. The transient absorption spectrum of the silene is broadened and red-shifted markedly in the latter solvent compared t...