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

Abstract

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).

Orientational effects in alkanone, alkanal or dialkyl carbonate + alkane mixtures and in alkanone + alkanone or + dialkyl carbonate systems

“…This supports that orientational effects are similar for all the systems studied with the CO or the CHO groups. In contrast, such a general behavior is not observed in ether + heptane systems [12], as it is shown in Fig. 4 for various systems of this type realized using data reported earlier [12].…”

“…(1) is useful when treating mixtures; see below). The so-called geometrical parameter of the mixture, 12…”

“…We are engaged in a systematic investigation on orientational effects (i.e., non-random mixing) in mixtures of organic liquids by means of the application of different models, such as: DISQUAC [1], ERAS [2], Flory [3], Kirkwood-Buff integrals [4,5] or the (0) CC S (concentration-concentration structure factor) formalism [6]. In this framework, along a series of works, we have shown that the Flory model is suitable to gain insight into orientational effects present in systems of the type: 1-alkanol + linear alkanone [7], or + nitrile [8], or + linear or cyclic ether [9,10]; 1-butanol + alkoxyethanol [11], alkoxyethanol + dibutyl ether [11], oxaalkane + alkane [12], or + aromatic compound [13]. Now, we extend these previous studies to alkanone, or alkanal or linear organic carbonate + alkane mixtures.…”

Thermodynamics of (ketone+amine) mixtures. Part VI. Volumetric and speed of sound data at (293.15, 298.15, and 303.15)K for (2-heptanone+dipropylamine, +dibutylamine, or +triethylamine) systems

“…However, if one takes into account that V E m of (TEA + n-alkane) systems decreases from heptane [36,39] [45] (all values in cm 3 Á mol À1 ). This variation is just the opposite to that for H E m and reveals the existence increasing structural effects when the number of the (CH 2 CH 2 O) groups of the polyether is increased [46]. Thus, the @V E m @T P values are positive, e.g., for, 2,5,8-trioxanonane, 0.0028 cm 3 Á mol À1 Á K À1 [43], and negative, À0.0025 cm 3 Á mol À1 Á K À1 [47], for the system containing the pentaether.…”

Volumetric Properties of Binary Mixtures of 1,2-Dichloroethane with Polyethers from (283.15 to 333.15) K and at Atmospheric Pressure

“…An analysis of each of the three contributions to the excess molar volume, V E , for all of the mixtures, shows that the interactional contribution is predominant and always negative. Moreover, the magnitude of the interactional and the “free volume” contributions increases with the increase of size and dipole moment, μ i /D of the polyether (1.71 for EGDME, 1.97 for DEGDME, and 1.92 for DEGDEE), while the magnitude of the “free volume” contribution, the lowest, remains constant.…”