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 Δ h G O , enthalpy of hydration Δ h H O , heat capacity of hydration Δ h Cp O , and volume V 2 O , 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: CH 3, CH 2, CH, C for saturated hydrocarbons; c-CH 2, c-CH, c-C for cyclic saturated hydrocarbons; CH ar, C ar 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 Δ h G O , Δ h H O , Δ h Cp O , and V 2 O at 298.15 K, 0.1 MPa for many hydrocarbons involved in geochemical and environmental processes.