Orientational Effects and Random Mixing in 1-Alkanol + Alkanone Mixtures

1-Alkanol + alkanone systems have been investigated through the data analysis of molar excess functions, enthalpies, isobaric heat capacities, volumes and entropies, and using the Flory model and the formalism of the concentrationconcentration structure factor (SCC(0)). The enthalpy of the hydroxyl-carbonyl interactions has been evaluated. These interactions are stronger in mixtures with shorter alcohols (methanol-1-butanol) and 2-propanone or 2-butanone. However, effects related to the self-association of alcohols and to solvation between unlike molecules are of minor importance when compared with those which arise from dipolar interactions. Physical interactions are more relevant in mixtures with longer 1-alkanols. The studied systems are characterized by large structural effects. The variation of the molar excess enthalpy with the alcohol size along systems with a given ketone or with the alkanone size in solutions with a given alcohol are discussed in terms of the different contributions to this excess function. Mixtures with methanol show rather large orientational effects. The random mixing hypothesis is attained to a large extent for mixtures with 1-alkanols ≠ methanol and 2-alkanones. Steric effects and cyclization lead to stronger orientational effects in mixtures with 3-pentanone, 4-heptanone, or cyclohexanone. The increase of temperature weakens orientational effects. Results from SCC(0) calculations show that homocoordination is predominant and support conclusions obtained from the Flory model.Ministerio de Ciencia e Innovación, under Project FIS2010-1695

Enthalpies de mélange des α, ω-dichloroalcanes avec des hydrocarbures

Les auteurs rapportent les enthalpies d’excès, hE, des mélanges binaires suivants : de l’heptane n avec le 1,3-dichloropropane, le 1,4-dichlorobutane, le 1,5-dichloropentane et le 1,6-dichlorohexane ; du benzène avec le 1,3-dichloropropane, le 1,4-dichlorobutane, le 1,5-dichloropentane et le 1,6-dichloro- hexane. Les données expérimentales sont interprétées en utilisant les équations dérivées du modèle réticulaire, en ternies d’interaction entre surfaces moléculaires, dans l’approximation quasi chimique. La comparaison des valeurs de hE ainsi calculées avec les valeurs expérimentales fait apparaître l’existence d’une interaction intramoléculaire chlore-chlore dans les α,ω-dichloroalcanes, croissante avec le rapprochement des atomes de chlore

Volumetric properties of, and ion-pairing in, aqueous solutions of alkali-metal sulfates under superambient conditions

Apparent molar volumes for Na2SO4(aq) and K2SO4(aq) have been obtained from our recent densitometric measurements and selected experimental data from literature at temperatures up to 573 K and pressures up to 30 MPa. The Pitzer ion-interaction model was used to correlate the data in order to obtain recommended values as a function of temperature, pressure and concentration and to yield partial molar volumes at infinite dilution. By comparison with the volumetric data of other strong electrolytes, and consistent with their reported ion-association constants, the present data indicate that ion-pairing is significant for Na2SO4(aq) and K2SO4(aq) at higher temperatures. A semiquantitative treatment is presented which enables the partial molar volumes of 1 : 2 (and 2 : 1) electrolytes to be corrected for the effects of ion-pairing

Volumetric behavior of aqueous NaF and KF solutions up to 350°C and 30 MPa

The volumetric behavior of NaF(aq) and KF(aq) has been studied as a function of temperature up to 627 K and pressures up to 30 MPa using a vibrating-tube flow densitometer. The measured densities were used to derive apparent molar volumes VΦ at concentrations up to 0.9 mol-kg-1 for NaF and up to 3 mol-kg-1 for KF. Standard partial molar volumes V2o[(NaF)-and V2o((KF) were obtained by extrapolating VΦ values to infinite dilution using the Pitzer equation truncated at the second virial coefficient. Comparison with related 1:1 and 1:2 electrolytes allows examination of the extent to which the concentration and temperature dependence of the volumes is linked with the size and charge of ions. A semiquantitative estimate of association based on the close similarity of fluorides and hydroxides is made to evaluate the effect of ion-pairing on the volumetric behavior of the fluorides

Enthalpies de mélange des chlorures organiques avec des hydrocarbures

Les auteurs rapportent les enthalpies de mélange des systèmes binaires suivants : 1-chlorobutane avec l’heptane n, le décane n, l’hexadécane n, le benzène, le toluène, l'éthyl-benzène, le propylbenzène et le butylbenzène ; chloroben- zène, chloromélhylbenzène et (2-chloroéthyl)benzène. avec l’heptane n. Les données expérimentales sont interprétées en utilisant des équations dérivées essentiellement du modèle réticulaire, mais en termes d’interaction entre surfaces moléculaires dans l’approximation quasi chimique.Les enthalpies d’excès expérimentales de presque tous les systèmes étudiés ont pu être reproduites à l’aide de deux paramètres caractérisant les surfaces de contact du benzène ft du chlore, et de 3 paramètres représentant les enthalpies d’interéchange des paires de surface de contact : aliphatique/aromatique, aliphatique /chlore, aromatique /chlore.On constate l’effet inductif du groupement alkyl sur les interactions entre les hydrocarbures aromatiques substitués et les chlorures aliphatiques, ainsi que la forte interaction filtre l’atome de chlore et le noyau benzénique du chloro- benzène

Thermodynamics of organic mixtures. A generalized quasichemical theory in terms of group surface interactions

A general quasi chemical theory in terms of group surface interactions is presented. The theory is applied to several basic classes of organic mixtures comprising n-alkanes, aromatic hydrocarbons, cyclohexane, tetrachloromethane, ethers and chloroalkanes. Interchange Gibbs energies and enthalpies are tabulated for ten contact pairs. Comparison with experimental Gibbs energies and enthalpies shows quite satisfactory agreement for all of the systems investigated. Possible sources of discrepancy and ways of refining the model are discussed