Inmaculada Velasco

Thermodynamics of mixtures containing iodoalkanes. II. Excess enthalpies of mixtures of 1-iodoalkane + cyclohexane, + benzene, or + tetrachloromethane. Measurement and analysis in terms of group contributions (DISQUAC)

Abstract Molar excess enthalpies H E at 298.15 K and atmospheric pressure are reported for 15 binary liquid mixtures of 1-iodoalkanes (iodomethane, iodoethane, 1-iodobutane, 1-iodoheptane and 1-iodododecane) and three solvents: cyclohexane (C 6 H 12 ), benzene (C 6 H 6 ) or tetrachloromethane (CCl 4 ). These experimental results along with literature data on liquid—vapor equilibria (excess molar Gibbs energies) and activity coefficients at infinite dilution are interpreted in terms of the DISQUAC group contribution model. Each class of systems is characterized by three types of groups or contact surfaces: iodine (I) and alkane, in 1-iodoalkanes, and solvent. The interchange energies of the alkane/solvent and alkane/I contacts were determined independently from the study of solvent + n-alkane and 1-iodoalkane + n-alkane systems, respectively. The interchange energies of the solvent/I contacts were estimated in this work. Qualitatively, the properties of 1-iodoalkanes are similar to those of 1-bromoalkane in the same solvents. In C 6 H 12 , the main contribution to the excess functions is given by the quasi-chemical term equal C 6 H 12 /I and alkane/I interaction parameters. The dispersive C 6 H 12 /I parameters are smaller than the alkane/I parameters and are independent of the chain length of the 1-iodoalkane. The solutions in C 6 H 6 and CCl 4 exhibit the characteristic features of polar solute + polarizable solvent mixtures, viz., the deviations from ideality are less positive than in alkanes, the experimental H E curves are asymmetrical, may be S-shaped with CCl 4 , and are best reproduced when the solvent/I contact is taken entirely dispersive. The dispersive C 6 H 6 /I and CCl 4 /I parameters vary regulary with the chain length of the 1-iodoalkane. In general, the model represents the available experimental H E data almost within the limits of errors, if the conformational contribution is properly taken into account.

Estimation des enthalpies de vaporisation des composes organiques liquides. Partie 2. Applications aux ethersoxydes, thioalcanes, cetones et amines

Abstract In a recent publication it was shown that the method of Bensons group permitted the estimation of the enthalpies of vaporisation for organic monofunctional compounds. The present paper includes molecules of the type R 1 —X—R 2 with X = O, S, CO, and primary, secondary and tertiary amines. Calculations are also reported for mono- and disubstituted derivatives of 1,2 dihydroxyethane and acetals.

Excess enthalpies of 1-chloroalkane + benzene. Measurement and analysis in terms of group contributions (DISQUAC).

Abstract Molar excess enthalpies, H E , at 298.15 K and atmospheric pressure are reported for 7 binary liquid mixtures of 1-chloroalkanes (1-chloropropane, 1-chlorobutane, 1-chlorohexane, 1-chlorooctane, 1-chlorodecane, 1-chlorododecane and 1-chlorohexadecane) + benzene. These experimental results along with literature data on liquid—vapor equilibria (excess molar Gibbs energies, G E ) and activity coefficients at infinite dilution are interpreted in terms of the DISQUAC group contribution model. This class of systems is characterized by three types of groups or contact surfaces: chlorine (C1) and alkane, in 1-chloroalkanes, and benzene (C 6 H 6 ). The interchange energies of the alkane/C 6 H 6 and alkane/C1 contacts were determined independently from the study of C 6 H 6 + n-alkane and 1-chloroalkane + n-alkane systems, respectively. The interchange energies of the C 6 H 6 /Cl contact were estimated in this work. The 1-chloroalkane solutions in C 6 H 6 exhibit the characteristic features of polar solute + polarizable solvent mixtures, viz., the deviations from ideality are less positive than in alkanes, may be even negative, the experimental G E and H E curves are asymmetrical, often S-shaped, and are best reproduced when the C 6 H 6 /Cl contact is taken entirely dispersive. The dispersive C 6 H 6 /Cl parameters vary in the same regular manner with the chain length of the 1-chloroalkane as observed previously for 1-bromoalkane or 1-iodoalkane + benzene mixtures. In general, the model represents the available experimental G E and H E data almost within the limits of errors, if the “conformational” contributions of the long-chain alkyl/C 6 H 6 contact is taken into account.

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 enthalpies of some binary mixtures. Contribution to the study of the BrO specific interaction

Excess enthalpies of n-hexane + 1-bromohexane, + methylbutylketone, + 1,2-dimethoxyethane, and + acetylacetone; cyclohexane + bromocyclohexane, + di-n-propylether, + methylbutylketone, + 1,2-dimethoxyethane, and + acetylacetone; and 1-bromohexane or bromocyclohexane+din-propylether, + methylbutylketone, + 1,2-dimethoxyethane, and + acetylacetone, at 303.15 K, have been measured as a function of composition. The results for HE of n-hexane+ether or + ketone show the different influence on the excess enthalpy of a repeated functional group in the molecule. In the mixtures containing 1-bromohexane or bromocyclohexane a specific interaction BrO, of acceptor-donor type, exists. Similar conclusions can be obtained from the cyclohexane mixtures; HE is higher, except for 1,2-dimethoxyethane+cyclohexane, than the corresponding n-hexane mixtures, and this can be attributed to dispersive aliphatic-cycloaliphatic interactions.

Estimation of DISQUAC interchange energy parameters for n-alkylamine + n-alkane mixtures

Abstract Velasco I., Fernandez J., Otin S. and Kehiaian H.V., 1991. Estimation of DISQUAC interchange energy parameters for n-alkylamine + n-alkane mixtures. Fluid Phase Equilibria, 69:15-32. The experimental literature data on vapor-liquid equilibria, molar excess Gibbs energies, molar excess enthalpies and activity coefficients at infinite dilution of n-alkylamine + n-alkane mixtures are interpreted in terms of the DISQUAC group contribution model. The systems are characterized by two types of groups or contact surfaces: alkane (CH3, CH2) and amine (NH2). Interchange coefficients of the n-alkylamine + n-alkane mixtures, calculated from experimental G e and H e values, show a variation in the case of short-chain n-alkylamines with the number of C atoms u, obtaining a constant value for n-alkylamines with u ⩾ 4. The model reproduces most of the experimental data quite well and predicts the partial miscibility for methylamine + n-alkanes at low temperatures. The experimental liquid-liquid equilibrium curves of ammonia + n-alkanes may be also calculated using the interchange coefficients of the amines extrapolated to u = 0.

Water dew points of binary nitrogen+water and propane+water mixtures. Measurement and correlation

Abstract A water dew point generation bench has been built and tested. Experimental measurements of dew point for binary nitrogen+water and propane+water were carried out between 1.01×105 Pa and 109.61×105 Pa and temperatures from 249.80 to 283.93 K. An excess function–equation of state method reproduces quite accurately the experimental curves independently of the pressure range.

Excess enthalpies of binary mixtures containing α,ω-dibromoalkanes. Measurement and analysis in terms of group contributions (disquac)

Abstract Arial, M., Munoz, Embid J., Otin, S., Velasco, I. and Kehiaian, H.V., 1991. Excess enthalpies of binary mixtures containing α,ω-dibromoalkanes. Measurement and analysis in terms of group contributions (DISQUAC).

Excess enthalpies and molecular interactions in solutions of 1-fluoroalkanes in alkanes, benzene or tetrachloromethane. A group contribution (DISQUAC) study

Molar excess enthalpies HE at 298.15 K and atmospheric pressure were determined for 12 binary liquid mixtures, 1-fluoropentane, 1-fluorohexane, or 1-fluorononane + a non-polar solvent (hexane, cyclohexane, benzene, or tetrachloromethane) and were interpreted by the DISQUAC group contribution model. 1-Fluoroalkane + n-alkane mixtures are characterized by two types of groups or contact surfaces, fluorine (F) and alkane (CH3, CH2), the remaining mixtures by the additional contact surfaces of the solvents (C6H12 C6H6, or CCl4). The interchange energies, entirely dispersive, of the alkane-solvent contacts were determined independently from the study of solvent-alkane mixtures. The dispersive F-alkane parameters were assumed to equal the parameters of perfluoroalkanes + n-alkanes. The shape of the HE curves of 1-fluorolkane + polarizable solvent (C6H6, CCl4) mixtures are best reproduced by the model when the quasi-chemical F-solvent parameters are assumed to equal zero. The quasi-chemical F-alkane (the same for n-alkanes and cyclohexane) and the dispersive F-solvent parameters were estimated in this work. The 1-fluoroalkane solutions in C6H6 or CCl4 exhibit the characteristic features of polar solute + polarizable solvent mixtures, viz., the deviations from the ideality are less positive than in alkanes and the experimental HE curves are strongly asymmetrical.

Thermodynamic properties of organic oxygen compounds excess enthalpies for some ester + hexane or + 1-bromohexane, and bromoester + hexane mixtures

Abstract Excess enthalpies of hexane + methyl acetate, +ethyl acetate, +isopropyl acetate, + tert -butyl acetate, +methyl propionate, +ethyl propionate, + tert -butyl propionate, +methyl butyrate, +ethyl-3-bromopropionate, +ethyl-2-bromobutyrate, or +ethyl-4-bromobutyrate, and 1-bromohexane +ethyl acetate, +ethyl propionate, or +methyl butyrate, have been measured at 303.15 K as a function of composition. The results obtained show an increase of H E when the length of either the alcoholic or the acid radical of the ester decreases. In the investigated (aliphatic ester + 1-bromohexane) mixtures the contribution of the specific BrO(carboxylate) interaction to H E seems to be of roughly the same size as the BrO(carbonyl group) one, and in the (bromoester + hexane) mixtures the intramolecular BrO interaction increases as the separation between the bromine atom and the carboxylate group decreases.