THERMODYNAMIC FUNCTIONS OF HYDRATION OF HYDROCARBONS AT 298.15 K AND 0.1 MPA

Abstract

An extensive compilation of experimental data yielding the infinite dilution partial molar Gibbs energy of hydration ΔhGO, enthalpy of hydration ΔhHO, heat capacity of hydration ΔhCpO, and volume V2O, at the reference temperature and pressure, 298.15 K and 0.1 MPa, is presented for hydrocarbons (excluding polyaromatic compounds) and monohydric alcohols. These results are used in a least-squares procedure to determine the numerical values of the corresponding properties of the selected functional groups. The simple first order group contribution method, which in general ignores nearest-neighbors and steric hindrance effects, was chosen to represent the compiled data. Following the precedent established by Cabani et al. (1981), the following groups are considered: CH3, CH2, CH, C for saturated hydrocarbons; c-CH2, c-CH, c-C for cyclic saturated hydrocarbons; CHar, Car for aromatic hydrocarbons (containing the benzene ring); C=C, C≡C for double and triple bonds in linear hydrocarbons, respectively; c-C=C for the double bond in cyclic hydrocarbons; H for a hydrogen atom attached to the double bond (both in linear and cyclic hydrocarbons) or triple bond; and OH for the hydroxyl functional group. In addition it was found necessary to include the “pseudo”-group I(C-C) to account for the specific interactions of the neighboring hydrocarbon groups attached to the benzene or cyclic ring (in the latter case only for cis-isomers). Results of this study, the numerical values of the group contributions, will allow in most cases reasonably accurate estimations of ΔhGO, ΔhHO, ΔhCpO, and V2O at 298.15 K, 0.1 MPa for many hydrocarbons involved in geochemical and environmental processes.