Topological Investigations of Excess Heat Capacities of Binary and Ternary Liquid Mixtures Containing o-Chlorotoluene, Amides and Cyclohexane at 298.15, 303.15 and 308.15 K

Abstract

Excess heat capacities, $$ \left( {C_{p}^{\text{E}} } \right)_{12} $$ and $$ \left( {C_{p}^{\text{E}} } \right)_{123} $$ , of binary tetrahydropyran (1) + N-methylformamide or N,N-dimethylformamide or cyclohexane (2), o-chlorotoluene (1) + cyclohexane (2), and ternary o-chlorotoluene (1) + tetrahydropyran (2) + N-methylformamide or N,N-dimethylformamide or cyclohexane (3) mixtures have been determined from their measured heat capacities, $$ \left( {C_{p}^{{}} } \right)_{{\text{mix}}} $$ and $$ \left( {C_{p}^{\text{E}} } \right)_{123} $$ , at 298.15, 303.15 and 308.15 K. The $$ \left( {C_{p}^{\text{E}} } \right)_{12} $$ and $$ \left( {C_{p}^{\text{E}} } \right)_{123} $$ values have been correlated using the Redlich–Kister equation to show their dependence on composition. The excess heat capacities, $$ \left( {C_{p}^{\text{E}} } \right)_{12} $$ , give information about the degree of non-randomness in the mixture. In this context, non-randomness contributes positively to $$ \left( {C_{p}^{\text{E}} } \right)_{12} $$ whereas randomness results in negative $$ \left( {C_{p}^{\text{E}} } \right)_{12} $$ values. The connectivity parameters of third degree, 3 ξ, of the constituent molecules, which in turn deal with topology, have been utilized (Graph theory) to compute $$ \left( {C_{p}^{\text{E}} } \right)_{12} $$ and $$ \left( {C_{p}^{\text{E}} } \right)_{123} $$ values of the investigated mixtures. The experimental $$ \left( {C_{p}^{\text{E}} } \right)_{12} $$ and $$ \left( {C_{p}^{\text{E}} } \right)_{123} $$ values compare well with those calculated from Graph theory. The excess heat capacities, $$ \left( {C_{p}^{\text{E}} } \right)_{12} $$ and $$ \left( {C_{p}^{\text{E}} } \right)_{123} $$ of binary and ternary mixtures have also been analyzed in terms of Flory’s theory.