Thermodynamics of mixtures containing amines. XVII. Excess molar enthalpy and volume measurements for benzylamine + heptane or + 1-alkanol mixtures at 298.15 K. Application of the DISQUAC and ERAS models

Abstract

Excess molar enthalpies, $H_{\text{m}}^{\text{E}}$, at 298.15 K and 0.1 MPa have been measured by means of a Tian-Calvet microcalorimeter for the systems benzylamine (phenylmethanamine) + heptane, or + methanol, or + 1-propanol, or + 1-pentanol, or + 1-heptanol, or + 1-decanol. In addition, excess molar volumes, $V_{\text{m}}^{\text{E}}$, at the same conditions have been also determined using a densimeter Anton Paar model DSA 5000 for the benzylamine + heptane mixture. The $H_{\text{m}}^{\text{E}}$ of this solution is large and positive since at 298.15 K the system temperature is close to its upper critical solution temperature. Thus, systems with n-alkanes show positive deviations from the Raoult's law. The measured $|V_{\text{m}}^{\text{E}}|$ values are low, indicating the existence of large structural effects. $H_{\text{m}}^{\text{E}}$ values of mixtures involving 1-alkanols are large and negative. That is, interactions between unlike molecules are dominant and the systems are characterized by negative deviations from Raoult's law. It is shown that the enthalpy of the hydrogen bonding between molecules of 1-alkanol and benzyalmine are more negative than those between 1-alkanol molecules. The $V_{\text{m}}^{\text{E}}$ values of the systems with 1-alkanols are also large and negative, and are determined mainly by interactional effects since they increase in line with $H_{\text{m}}^{\text{E}}$ and with the alcohol size. The different contributions to $H_{\text{m}}^{\text{E}}$ have been evaluated. The systems have been studied using the DISQUAC and ERAS models. ERAS describes correctly the $V_{\text{m}}^{\text{E}}$ function. DISQUAC largely improves ERAS results on $H_{\text{m}}^{\text{E}}$ or on excess molar heat capacities at constant pressure for the mixtures with 1-alkanols, which underlines that physical interactions are very relevant in such solutions.

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