Thermodynamics of mixtures involving some (benzene derivatives + benzonitrile) E. Calvo-Iglesias a, * , R. Bravo a , M. Pintos a , A. Amigo a , A.H. Roux b , G. Roux-Desgranges b a Departamento de Fı ´sica Aplicada, Facultad de Fı ´sica, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela, Spain b Thermodynamique des Solutions et des Polyme ` res, UMR CNRS 6003, Universite ´ Blaise Pascal, 63177 Aubie `re cedex, France Received 21 July 2006; received in revised form 7 September 2006; accepted 8 September 2006 Available online 22 September 2006 Abstract Interactions of binary mixtures involving some benzene derivatives (ethylbenzene, o-, m-, p-xylene, isopropylbenzene, 1,2,4-trimeth- ylbenzene, 1,3,5-trimethylbenzene, and methoxybenzene) with benzonitrile were investigated in continuation of our previous studies on binary systems (benzene or toluene + benzonitrile). Heat capacities by volume unit, determined with a Picker flow calorimeter at T = 298.15 K, and densities, measured by using Picker vibrating densimeters at the temperatures (298.15 and 308.15) K, are reported. Measurements were made over the entire range of mole fraction. From the primary measurements, the corresponding excess quantities V E and C E p;m are obtained. The magnitude of these experimental quantities together with H E literature data is discussed in terms of the nature and type of intermolecular interactions in binary mixtures. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Density; Heat capacity; Benzonitrile; Benzene derivatives 1. Introduction The interactions between aromatic molecules and ben- zonitrile have been the subject of many investigations, par- ticularly through the analysis of the thermodynamic properties of liquid mixtures [1–9]. The most striking fea- ture in this kind of system is the M-shaped curve of the excess enthalpies as can be observed, for example, in the mixtures of benzonitrile with toluene or benzene [1,5]. This unusual behaviour can be explained by the complex forma- tion between benzonitrile and either benzene or toluene. Most of the benzene derivatives would probably lead to a complex formation with benzonitrile, as suggested by some authors [2,3,9]. The negative values of excess molar enthal- pies in the (anisole + benzonitrile) system reported by Viswanathan et al. [3] coincide with those reported by Rajkumar et al. [9], who concluded that specific interac- tions between molecules take place in this mixture leading to complex formations with anisole molecules acting as the donor. The formation of charge-transfer complexes in mix- tures of benzonitrile with xylene isomers, ethylbenzene and mesitylene was reported by Letcher and Naicker [2]. The excess enthalpies in these mixtures are always positive and their low values indicate a strong association between benzonitrile and the aromatic compounds. In this work, we report isobaric excess molar heat capac- ities, C E p;m , at T = 298.15 K and excess molar volumes, V E , at T = 298.15 K and T = 308.15 K for {benzonitrile + eth- ylbenzene, o-, m-, p-xylene, isopropylbenzene (cumene), 1,2,4-trimethylbenzene (pseudocumene), 1,3,5-trimethyl- benzene (mesitylene), and methoxybenzene (anisole)}. The aim of this research is to compare the modifications of V E and C E p;m in binary systems containing different ben- zene derivatives and to analyze the thermodynamic behav- iour of these mixtures while also taking the literature values of excess enthalpies into account. 0021-9614/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jct.2006.09.007 * Corresponding author. Tel.: +34 981563100; fax: +34 981520676. E-mail address: faencina@usc.es (E. Calvo-Iglesias). www.elsevier.com/locate/jct J. Chem. Thermodynamics 39 (2007) 561–567