Enthalpic determinations of aliphatic ester-solvent systems with correlations

Abstract

Calorimetric measurements were carried out on ester-solvent systems where the esters were H(CH₂)_xCOO(CH₂)_yH, with x and y varying from 1 to 5, and the solvents were n-hexane and 1,2-dichloroethane. Calculation of the enthalpies of cavity formation enabled the enthalpies of interaction to be determined. Both enthalpies correlated with number of carbon atoms N, equal to x+y in the esters, giving for 1,2-dichloroethane

$$\begin{gathered} \Delta _{cav} H_m^O = 29.4 \pm 2.3 + 4.7 \pm 0.4N \hfill \\ \Delta _{int} H_m^O = - 53.9 \pm 2.5 - 8.2 \pm 0.5N \hfill \\ \end{gathered} $$

and for n-hexane

$$\begin{gathered} \Delta _{cav} H_m^O = 8.8 \pm 1.1 + 3.4 \pm 0.2N \hfill \\ \Delta _{int} H_m^O = - 20.0 \pm 2.1 - 8.3 \pm 0.4N \hfill \\ \end{gathered} $$

From these linear correlations enthalpies of an aliphatic ester, for example, the enthalpy of vaporization can be calculated by using a thermochemical cycle. The presence of chloro atoms in the aliphatic solvent causes a large interactive effect between the ester and 1,2-dichloroethane.