Strain Effects in Phenyl-Substituted Methanes. Geminal Interaction between Phenyl and the Electron-Releasing Substituent in Benzylamines and Benzyl Alcohols

The standard ( p ° = 0.1 MPa) molar enthalpies of formation Δ f H ° m (l) at T = 298.15 K of N, N -dimethylbenzylamine, α-methylbenzylamine, and α,α-dimethylbenzylamine were determined by means of combustion calorimetry. The standard molar enthalpies of vaporization of these compounds and also of benzylamine, benzyl alcohol, and α,α-dimethylbenzyl alcohol were obtained from the temperature dependence of the vapor pressure measured in a flow system. Resulting values of Δ f H ° m (g) were obtained at T = 298.15 K and used to derive strain enthalpies of benzyl derivatives. The intramolecular interactions of the substituents were discussed in terms of deviations of Δ f H ° m (g) from the group additivity rules. These values provide a further improvement on the group-contribution methodology for estimation of the thermodynamic properties of organic compounds.