Phase diagram and thermal properties of organic analogues of nonmetal–nonmetal systems

Abstract

The solid–liquid phase equilibrium data on three binary organic systems, namely 4-hydroxy benzaldehyde (HB)–2-methyl-4-nitro aniline (MNA), 3-hydroxy-4-methoxybenzaldehyde (HMB)–2-chloro-4-nitroaniline (CNA) and 4-aminobenzophenone (ABP)–m-nitrobenzoic acid (NBA), determined by the thaw-melt method, show the formation of a eutectic at 0.60 mol fraction of HB, 0.48 mol fraction of HMB and 0.51 mol fraction of ABP. These systems are organic analogue of nonmetal–nonmetal system. The values of enthalpy of fusion of eutectics and parent components were determined by the DSC method. Using the heat of fusion values, entropy of fusion, heat of mixing, excess thermodynamic functions and Jackson’s roughness parameter were calculated. The negative values of enthalpy of mixing in each case suggest the associative interaction between the molecules of the eutectic melt. The positive value of excess free energy for HB–MNA system indicates the associative interaction between like molecules, while the negative values of excess free energy for HMB–CNA and ABP–NBA indicate the associative interaction between unlike molecules.