arXiv subjects

Susana Villa

Publications and source records attributed to Susana Villa.

3 recordsLinked to original sources

arXiv2026

Thermodynamics of 2-undecanone + n-alkane mixtures

Densities and excess molar volumes ($V_{\text{m}}^{\text{E}}$) at (293.15-303.15) K and excess molar enthalpies ($H_{\text{m}}^{\text{E}}$) at 298.15 K are reported for 2-undecanone + heptane, or + octane, or + decane, or + dodecane, or + tetradecane mixtures at 95 kPa. Densities and $H_{\text{m}}^{\text{E}}$ were measured using, respectively, a densitometer Anton Paar DMA 602 and a Tian-Calvet micro-calorimeter. $H_{\text{m}}^{\text{E}}$ results are positive, indicating that interactions between like molecules are dominant. Both $H_{\text{m}}^{\text{E}}$ and $V_{\text{m}}^{\text{E}}$ increase in line with $n$ (number of C atoms of the alkane), which reveals that the increase of $V_{\text{m}}^{\text{E}}$ can be ascribed to an increased interactional contribution. Nevertheless, systems with $n$ = 7,8 show negative $V_{\text{m}}^{\text{E}}$ values, which reveals that $V_{\text{m}}^{\text{E}}$ is determined mainly by structural effects. Isochoric excess molar internal energies ($U_{V\text{m}}^{\text{E}}$) at 298.15 K have been obtained from the present $H_{\text{m}}^{\text{E}}$ and $V_{\text{m}}^{\text{E}}$ data. At equimolar composition, $U_{V\text{m}}^{\text{E}}$is nearly constant for $n$ = 7-10, and then slightly increases. This has been explained in terms of a possible folding of 2-undecanone. From the comparison of $U_{V\text{m}}^{\text{E}}$ results for similar systems involving n-alkanoates, it is shown that folding is more likely in solutions with these compounds.

physics.chem-ph↗

arXiv2026

Excess molar enthalpies of (iodobenzene, or 1-iodonaphthalene + n-alkane) liquid mixtures at T = 298.15 K and p = 93 kPa

Excess molar enthalpies ($H_{\text{m}}^{\text{E}}$) for iodobenzene, or 1-iodonaphthalene + heptane, + decane, + dodecane, or + tetradecane mixtures at 298.15 K and 93 kPa have been measured using a Tian-Calvet micro-calorimeter. The values of $H_{\text{m}}^{\text{E}}$ are positive and indicate that interactions between like molecules are prevalent. In contrast, our previous results on excess molar volumes ($V_{\text{m}}^{\text{E}}$) are negative for the systems C$_6$H$_5$I + heptane, or 1-iodonaphthalene + n-alkane, which reveal the existence of large structural effects in such solutions. This set of measurements has been used to determine isochoric excess molar internal energies ($U_{V\text{m}}^{\text{E}}$). In the range of n-alkanes considered (n is the number of C atoms of the alkane), values of $U_{V\text{m}}^{\text{E}}$ at equimolar composition decrease from n = 7 to n = 10 and then slightly increase for systems with C$_6$H$_5$I, while decrease slowly for mixtures with 1-iodonaphthalene. These trends fit well with the patterns observed for other alkane mixtures containing cyclic molecules. Dispersive interactions are dominant and those between aromatic molecules with a given halogen atom become stronger when the size of this atom increases due to the corresponding increase of molecular polarizability. The mixtures were studied using the DISQUAC and Flory models. The latter was also applied to n-alkane solutions with C$_6$H$_5$F, or 1-methylnaphthalene. Both theories describe accurately the $H_{\text{m}}^{\text{E}}$ data. In terms of the Flory model, this means that the random mixing hypothesis is largely achieved. On the other hand, the theory overestimates the interactional contribution to $V_{\text{m}}^{\text{E}}$, particularly for systems with C$_6$H$_5$X (X = F, I).

physics.chem-ph↗

arXiv2025

Liquid-liquid equilibria of systems containing 2-methoxyphenol or 2-ethoxyphenol and n-alkanes

Liquid-liquid equilibria phase diagrams have been determined for the systems: 2-methoxyphenol + n-decane, or + n-dodecane, or + n-tetradecane or + n-hexadecane and for 2-ethoxyphenol + n-octane, or + n-dodecane, or + n-tetradecane, or + n-hexadecane. The experimental method used is based on the observation, by means of a laser scattering technique, of the turbidity produced on cooling when a second phase appears. All the mixtures studied show an upper critical solution temperature, which increases with the n-alkane size. Dipolar interactions between like molecules become stronger in the sequence: 2-ethoxyphenol < 2-methoxyphenol < phenol. Data available in the literature suggest that this relative variation is also valid for n-alkane mixtures containing other substituted anilines, characterized by having a second polar group. The dependence of the upper critical solution temperature on the molecular structure of the polar aromatic compound involved is shortly discussed in terms of intramolecular and steric effects.

physics.chem-ph↗