Speeds of sound and density for binary mixtures of ethyl benzoate (EB) with N,N-dimethylformamide (NNDMF), N,N-dimethyl acetamide (NNDMAc), and N,N-dimethylaniline (NNDMA) were measured as a function of mole fraction at temperatures 303.15, 308.15？K, 313.15？K, and 318.15？K and atmospheric pressure. From the experimental data, adiabatic compressibility ( ), intermolecular free length ( ), and molar volume ( ) have been computed. The excess values of the above parameters were also evaluated and discussed in light of molecular interactions. Deviation in adiabatic compressibilities and excess intermolecular free length ( ) are found to be negative over the molefraction of ethyl benzoate indicating the presence of strong interactions between the molecules. The negative excess molar volume values are attributed to strong dipole-dipole interactions between unlike molecules in the mixtures. The binary data of , , and were correlated as a function of molefraction by using the Redlich-Kister equation. 1. Introduction The thermophysical study of esters is of increasing interest due to their wide range in flavouring, perfumery, artificial essences, and cosmetics. Esters are also important solvents in pharmaceutical, paint, and plastic industries [1]. Recently, interest in the study of liquid mixtures containing esters as one of the components [2–5] has increased. These studies are of great significance because one can get information regarding structural changes that occur in pure ester because of mixing. Among the different types of esters, ethyl benzoate (aromatic ester) is a polar solvent ( ) and is not a strongly associated liquid. On the other hand, NNDMF, to some extent, is associated by means of dipole-dipole interactions. Significant structural effects are absent due to the lack of hydrogen bonds. Therefore, it acts as an aprotic protophilic solvent [6]. NNDMAc is a dipolar aprotic solvent and is moderately structured [7]. The N,N-dialkylamides have no significant intermolecular hydrogen bonding capability but are highly polar with high percentage of ionic character, making oxygen of C=O group strongly negative [8]. NNDMA is a unassociated liquid [9]. The interactions of ethyl benzoate with N,N-dialkylamides and N,N-dimethylaniline are important to enable analysis of their dissimilar geometric structures on mixture properties. Rao [10] calculated the excess isentropic compressibilities for the binary mixtures of N,N-dimethylformamide and N,N-dimethylacetamide and various normal and branched esters. The negative excess values are attributed to the presence
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