Thermodynamic properties of mixtures of a dioxanonane isomer + n-octane at 298.15 k

Soejima, Hiroshi; Nakai, Hisaki; Tamura, Katsutoshi; Ogawa, Hideo; Murakami, Sachio; Toshiyasu, Yoshio

doi:10.1016/0040-6031(91)80106-s

Cited by 17 publications

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“…For mixtures including diethers (2,5-dioxahexane, 3,6dioxaoctane, or dioxanonane isomers) and heptane or octane, C p,m E is negative over all the composition range. [65][66][67] For solutions including ethers characterized by u ) 1 and V ) 2, 3, 4 and different alkanes, 64,[68][69][70] C p,m E shows a concentration dependence of the W-shape type: two minima at the extremes of the concentration range separated by a central maximum. This behavior is characteristic of systems at temperatures close to the UCST and is connected with dipolar interactions and with nonrandomness in the solution.…”

Section: Linear Polyether Systemsmentioning

confidence: 99%

Thermodynamics of Mixtures Containing Oxaalkanes. 4. Random Mixing and Orientational Effects in Ether + Alkane Systems

González

2010

Ind. Eng. Chem. Res.

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Molar excess enthalpies, H m E, and volumes, V m E, of linear or cyclic ether + n-alkane systems have been discussed in terms of the effective dipole moment, μ̅, of the ether, differences of standard enthalpies of vaporization of the ether and of the isomeric alkane, the number and relative positions of the oxygen atoms, the shape of the ether, and the relative size of the mixture compounds. The mentioned solutions have also been studied using the Flory model and the Kirkwood−Buff formalism. Both theories provide consistent results. At 298.15 K, the random mixing hypothesis is a good approximation for mixtures including linear or cyclic monoethers or linear diethers. Orientational effects become stronger in solutions with 2,5,8-trioxanonane, 2,5,8,11-tetraoxadodecane, or 2,5,8,11,14-pentaoxapentadecane. In the case of 1,3-dioxolane mixtures, this type of effect is more relevant than in systems with 1,4-dioxane. This is supported by W-shaped C p,m E curves, large variations of the Flory interaction parameter, X 12, with x 1, the oxaalkane concentration, and local mole fractions of the ether−ether type that are higher than the bulk ones, particularly at lower x 1 values. The latter means that orientational effects are more important at this condition, and this is confirmed by large X 12 variations with x 1 in the region of low x 1 values. At equimolar composition, X 12 values of solutions containing 2,5,8,11-tetraoxadodecane or cyclic ethers remain nearly constant with the number of C atoms of the alkane, which reveals that systems with such oxaalkanes are similar from an interactional point of view. From values of the internal excess energies at constant volume, U V m E, it is shown that interactions between like molecules are usually overestimated. Nevertheless, the general trends observed are independent of the H m E or U V m E data considered. Structural effects are present in mixtures with components that differ largely in size (e.g., dipropyl ether + hexadecane or 2,5,8,11,14-pentaoxapentadecane + hexane).

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