Celso Gutierrez Losa

Excess enthalpies of 1-iodoalkane + n-alkane mixtures. Measurement and analysis in terms of group contributions (DISQUAC)

Abstract Molar excess enthalpies at 303.15 K and atmospheric pressure are reported for 30 binary liquid mixtures of 1-iodoalkanes (iodomethane, iodoethane, 1-iodopropane, 1-iodobutane, 1-iodopentane, 1-iodohexane, 1-iodoheptane, 1-iodooctane, 1-iodododecane and 1-iodohexadecane) + n-alkanes (hexane, dodecane and hexadecane). These experimental results along with literature data on liquidvapour equilibria (excess molar Gibbs energies) and activity coefficients at infinite dilution are interpreted in terms of the DISQUAC group contribution model. The quasichemical interchange energies are the same for the whole series. The dispersive interchange energies of iodoethane and of all the higher 1-iodoalkanes are constant, but larger than for iodomethane. In general, the model reproduces the experimental data within the limits of errors. Larger discrepancies between the calculated and the experimental excess enthalpies are observed in mixtures of long-chain 1-iodoalkanes+short-chain n-alkanes. These may be attributed to conformational changes occurring in the long-chain 1-iodoalkane on mixing with the short-chain n-alkane. In contrast, it appears that 1-iodoalkanes do not significantly perturb the conformational equilibrium (or orientational order) in long-chain n-alkanes.

Excess volumes of 1,1,2,2-tetrachloroethane + tetrachloroethylene, and of 1,1,2,2-tetrachloroethane and of tetrachloroethylene + cyclohexane, + benzene, and + carbon tetrachloride at 303.15 K

Abstract Excess volumes of 1,1,2,2-tetrachloroethane + cyclohexane, + benzene, + carbon tetrachloride; of tetrachloroethylene + cyclohexane, + benzene, + carbon tetrachloride; and 1,1,2,2-tetrachloroethane + tetrachloroethylene, have been measured at 303.15 K by a dilatometric method. For benzene + 1,1,2,2-tetrachloroethane some measurements have also been carried out at 313.15 K. The results obtained are related with the H E measurements for the same mixtures.

Excess enthalpies of 1,1,2,2-tetrachloroethane + cyclohexane, + benzene, and + carbon tetrachloride and tetrachloroethylene + cyclohexane, + benzene, and + carbon tetrachloride at 303.15 K

Abstract The excess enthalpies of 1,1,2,2-tetrachloroethane + benzene, + cyclohexane, and + carbon tetrachloride and tetrachloroethylene + benzene, + cyclohexane, and + carbon tetrachloride were measured at 303.15 K. Mixing was endothermic except for 1,1,2,2-tetrachloroethane + benzene which was markedly exothermic. This exception is in agreement with the experimental evidence that the chlorine atom shows a specific interaction with aromatic molecules; there might also be a contribution from the formation of hydrogen bonds between the two components. Tetrachloroethylene + benzene is, however, strongly endothermic and the most plausible explanation of this behaviour is that the 3d level of the chlorine atoms has partially saturated its acceptor capacity with double-bond electrons.