Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

In this work we determine, both experimentally and computationally, structural and thermochemical properties of the methyl 2- and 4-methoxybenzoates. Combustion and vaporization enthalpies of these compounds were obtained experimentally through combustion calorimetry and thermogravimetry. From these properties, their standard molar enthalpies of formation in the gas-phase, at T = 298.15 K, were also determined. In addition, we computed gas-phase enthalpies of formation of methyl 2-, 3-, and 4-methoxybenzoates using the Gaussian G4 composite method, atomization reactions, and a weighted Boltzmann average. This average was performed over the stable conformers of each compound and the respective Gibbs energies were used to compute the weights for the Boltzmann average. The analyses of the electronic density of the molecules and of non-covalent interactions were performed as well. We found a good agreement between our experimental and computational enthalpies of formation of methyl 2- and 4-methoxybenzoates. Finally, we discuss the enthalpic effects, as a function of the relative position of the methoxy and methyl groups, upon the benzoate base-structure.