Stabilization energies for α- and β-silyl substituents on vinyl cations determined using mass spectrometric techniques

Vinyl cation stabilization energies in the gas phase of 29.5 kcal mol–1 for an α-trimethylsilyl substituent and 43.5 kcal mol–1 for a β-trimethylsilyl substituent relative to hydrogen are obtained from measurement of the appearance energies for metastable peaks for loss of I˙ from ionized Me3Si–ClCH2 and (E)-Me3Si–CHCHl respectively.