Phase diagram and association constants of a molecular complex in the 1,3,5-trinitrobenzene–benzene binary system

Abstract

The phase diagram of the binary system of the electron acceptor (A) 1,3,5-trinitrobenzene with the electron donor (D) benzene has been determined by differential scanning calorimetry. A termolecular, congruently melting complex AD₂ was found. Association constants of the complex in the molten state have been obtained from the analysis of the liquidus line of the complex in terms of concurrence of complexing and non-complexing interactions. The proton chemical shifts of 1,3,5-trinitrobenzene and benzene have been measured as a function of the concentration over the whole composition range of the A–D binary system in the molten state. The data were analysed by a multiparametric curve-fitting method. Fitting was performed for simple AD and AD₂ and double AD + AD₂ equilibrium models, each with and without non-complexing interactions. No reasonable fit could be obtained for the ideal association models. The inclusion of non-complexing interactions allowed the data to be fitted by either the simple AD or the double AD + AD₂ equilibrium model. The results are compared with those obtained from analysis of the phase diagram data.