ORIGINAL PAPER Study of molecular interactions in binary mixtures of 2-chloro- 4 0 methoxy benzoin with various solvents through ultrasonic speed measurements B Thanuja 1 , C Kanakam 2 * and G Nithya 1 1 Department of Chemistry, School of Engineering, Vels University, Pallavaram, Chennai 600 117, Tamil Nadu, India 2 Department of Chemistry, SRM Valliammai Engineering College, Kattankulathur 603 203, Tamil Nadu, India Received: 19 May 2013 / Accepted: 15 July 2013 Abstract: Density (q) and ultrasonic velocity (U), for binary mixtures of 2-chloro-4 0 -methoxy benzoin with ethanol, chloroform, acetonitrile, benzene and 1,4-dioxane of different compositions have been measured at 298 K and explanation of solute solvent interactions and effect of polarity of the solvent on type of interactions are presented in this paper. From the above data, adiabatic compressibility (b), intermolecular free length (L f ) and relative association (R A ) have been calculated. Other useful parameters such as excess density, excess velocity, excess intermolecular freelength and excess adiabatic compressibility have also been calculated. These parameters have been used to study the nature and extent of intermolecular interactions between component molecules in present binary mixtures. Keywords: Ultrasonic velocity; Density; Excess parameters; Intermolecular hydrogen bonding PACS Nos.: 43.35.-c; 43.35.Bf; 43.35.Cg 1. Introduction Study of intermolecular interaction plays an important role in development of molecular sciences. A large number of studies have been made on molecular interaction in liquid systems by various physical methods like Infrared spectra [1, 2], Raman effect [3], Nuclear Magnetic resonance [4], dielectric constant [5], ultra violet spectra [6] and ultra- sonic method [7, 8]. In recent years, ultrasonic technique has become a powerful tool in providing information regarding molecular behavior of liquids and solids owing to its ability of characterizing physicochemical behavior of the medium [9, 10]. The practical application of mixed solvents, rather than single solvent, in industrial and bio- logical processes has been recognized all over the world, as they provide a wide choice of solutions with appropriate properties [11]. Experimental studies aim at finding evi- dence for intermolecular interactions in binary liquid mixtures have been carried out by us [12, 13]. We focus in this paper, results of binary mixtures of 2-chloro-4 0 - methoxy benzoin (2C4 MB) with solvents of different polarity. The components of these binary mixtures (2C4 MB and various solvents) are interesting as they have proton donor as well as proton accepting ability. As a result, significant interaction through hydrogen bonding between unlike molecules in these binaries is expected. Also, it is worthwhile to examine the effect of solvent interaction between 2C4 MB and various solvents. We report results of ultrasonic study of molecular interactions of 2C4 MB at 298 K in ethanol, chloroform, acetonitrile, benzene and 1,4-dioxane binary mixtures. Ethanol is a highly polar but protic solvent. It is self associated through hydrogen-bonding. The solvent polarity decreases from ethanol to benzene. The intermolecular interaction varies from polar solvent to non-polar solvent. 2. Experimental details The solvents obtained were A R Grade and purified by standard procedures and their boiling points were measured to ascertain their purity [14, 15]. All solutions were pre- pared by mass in a dry box and kept in special air tight *Corresponding author, E-mail: csthanujacsrevathy@yahoo.co.in Indian J Phys DOI 10.1007/s12648-013-0364-7 Ó 2013 IACS