Thermochemical and theoretical studies of 4-methylbiphenyl, 4,4′-dimethylbiphenyl, 4,4′-dimethyl-2,2′-bipyridine

Abstract

The standard (p°=0.1 MPa) molar enthalpies of formation for 4-methylbiphenyl, 4,4′-dimethylbiphenyl and 4,4′-dimethyl-2,2′-bipyridine were derived from the standard molar enthalpies of combustion, in oxygen, at T=298.15 K, measured by static-bomb combustion calorimetry. The standard molar enthalpies of sublimation, at T=298.15 K, were measured by Calvet microcalorimetry. Theoretical calculations at the ab initio restricted Hartree–Fock (RHF) level with second-order Møller–Plesset (MP2) perturbation theory correlation corrections and density functional theory (DFT) have been carried out for all these molecules in order to access their stabilitites relative to the non-substituted ones. The theoretical results are in general good agreement with the experimental results.