α-C−H Bond Dissociation Energies of Some Tertiary Amines

The α-C−H bond dissociation energies of 14 tertiary, trialkyl- and arylalkylamines have been measured by photoacoustic calorimetry (PAC). In general, the data lead to an upward revision of the bond dissociation energies (BDE's). The effects of α-phenyl and α-vinyl substitution have been quantified for the first time. α-Phenyl substitution was found to have a significantly smaller effect on lowering α-C−H BDE's than α-vinyl substitution. These data provide a thermochemical confirmation of the stereoelectronic hypothesis proposed by Lewis et al. in 1982.