RT info:eu-repo/semantics/article
T1 N-Alkanoate + N-Alkane Mixtures: Folding of Hydrocarbon Chains of N-Alkanoates
A1 González López, Juan Antonio Mariano
A1 Hevia de los Mozos, Luis Fernando
A1 Sanz, Luis Felipe
A1 Lozano Martín, Daniel
A1 García de la Fuente, Isaías Laudelino
A1 Cobos Hernández, José Carlos
K1 Termodinámica
K1 n-alkanoates
K1 n-alkanes
K1 molar excess isochoric internal energy
K1 thermophysical models
K1 dispersive interactions
K1 structural effects
K1 folding
K1 2213 Termodinámica
AB The mixtures CH$_3$(CH$_2$)$_{u-1}$COO(CH$_2$)$_{v-1}$CH$_3$  ($u=5-13$, $v=1,2$; $u=1,2,3$, $v=3,4$; $u=1,2,4$, $v=5$) + n-alkane have been investigated using experimental data (viscosity and excess molar functions: enthalpy, $H_{\text{m}}^{\text{E}}$, volume, $V_{\text{m}}^{\text{E}}$, isobaric heat capacity, and isochoric internal energy, $U_{V\text{m}}^{\text{E}}$) and models (Flory, Grunberg-Nissan, Bloomfield-Dewan). They are characterized by weak orientational effects. Large structural effects are found in some systems, like those containing pentane. Some considerations from standard enthalpies of vaporization, cohesive energy densities and $V_{\text{m}}^{\text{E}}$ of heptane mixtures reveal the existence of structural changes in longer n-alkanoates, which lead to stronger interactions between them. The observed decrease of $H_{\text{m}}^{\text{E}}$ for systems with a given n-alkane seems to be more related to the steric hindrance of the COO group than to interactional effects. The $U_{V\text{m}}^{\text{E}}(n)$ function ($n=$ number of C atoms in the n-alkane) shows a minimum for systems with esters with ($u\geq4$, $v=1$); ($u\geq7$, $v=2$), or ($u\geq 1$, $v=4,5$). A similar dependence was found for n-alkane mixtures involving cyclic molecules (cyclohexane, benzene). This result suggests that certain n-alkanoates, in an alkane medium, can form quasi-cyclic structures. Viscosities are well described by means of free volume effects only. For systems with butyl ethanoate or methyl decanoate, the variation of $\Delta \eta (n)$ (deviation of dynamic viscosity) is consistent with that of $U_{V\text{m}}^{\text{E}}(n)$, which supports the existence of cyclic structures in these esters. The Flory model provides poor results on $H_{\text{m}}^{\text{E}}$ for systems with large structural effects. Results improve when the model is applied to $U_{V\text{m}}^{\text{E}}(n)$ data.
PB Springer Nature
SN 0095-9782
YR 2025
FD 2025-08-14
LK https://uvadoc.uva.es/handle/10324/78195
UL https://uvadoc.uva.es/handle/10324/78195
LA spa
NO J. Solution Chem. 54 (2025) 1403-1425
NO Producción Científica
DS UVaDOC
RD 03-oct-2025