Substituent effects. 5. Vinyl and ethynyl derivatives. An examination of the interaction of amino and hydroxy groups with carbon-carbon double and triple bonds

Abstract

The effect of substituents on the energies of vinyl derivatives was examined with the use of group separation reactions with ethane to give propene and a substituted methane. The energy changes for these reactions were much smaller than those found for a corresponding set of acetyl derivatives. The bond dissociation energies (BDEs) for the vinyl derivatives were found to be linearly related to those of the related methyl derivatives with a slope close to unity. The average difference between BDEs in the two series was 12.1±1.5 kcal/mol, with the larger values found in the vinyl series. This is in accord with the difference in hybridization between vinyl and methyl. The results for the vinyl series stand in marked contrast to the acetyl series previously studied