Thermodynamics of 2-alkanol + polar organic solvent mixtures. I. Systems with ketones, ethers or organic carbonates

Abstract

The mixtures 2-propanol or 2-butanol + n-alkanone, or + acetophenone or + linear monoether, or + cyclic ether, or + linear organic carbonate, or + propylene carbonate have been investigated using thermodynamic data, and in terms of the Flory theory, and the Kirkwood-Buff integrals. The data considered are: excess molar enthalpies ($H_{\text{m}}^{\text{E}}$), volumes, entropies, and the temperature dependence of $H_{\text{m}}^{\text{E}}$. The enthalpy of the 2-alkanol-solvent interactions have been determined, and the different contributions to $H_{\text{m}}^{\text{E}}$ are discussed. It is shown that $H_{\text{m}}^{\text{E}}$ values of the 2-alkanol (fixed) + n-alkanone, or + linear carbonate mixtures change in the same manner that for n-alkanone, or linear carbonate + n-alkane (fixed) systems. In contrast, $H_{\text{m}}^{\text{E}}$ values of 2-alkanol (fixed) + linear monoether or + n-alkane mixtures change similarly. This set of results suggests that solvent-solvent interactions are determinant in systems with n-alkanone or linear carbonate, while interactions between alcohol molecules are determinant in mixtures with linear monoethers. According to the Flory model, orientational effects in systems with a given 2-alkanol become weaker in the sequence: linear monoether > linear organic carbonate > n-alkanone, and are stronger in solutions with a cyclic monoether than in those with cyclic diethers, and in systems with acetophenone or propylene carbonate than in the mixtures with the corresponding linear solvents. Results obtained from the Kirkwood-Buff integrals are consistent with these findings. The application of Flory model reveals that orientational effects are similar in systems with 1- or 2-alkanols, with the exception of solutions with linear monoethers, where such effects are stronger in mixtures containing 1-alkanols.