Effect of temperature and solvents on thermo-physical properties of 1,3,4-oxadiazole derivative at atmospheric pressure D.R. Godhani ⁎, P.B. Dobariya, A.M. Sanghani, A.A. Jogel, J.P. Mehta Department of Chemistry, DST-FIST sponsored, Mahatma Gandhi Campus, Maharaja Krishnakumarsinhji Bhavnagar University, Bhavnagar-364022, Gujarat, India abstract article info Article history: Received 25 December 2012 Accepted 25 January 2013 Available online 12 February 2013 Keywords: Acoustical parameter Density Gibbs energy of activation Molecular interaction 1,3,4-Oxadiazole derivative Thermodynamic parameter The density (ρ), viscosity (η) and ultrasonic velocity (U) of pure solvents: chloroform (CF), N,N-dimethylformamide (DMF), solutions of 2-((4-acetyl-5-(4-bromophenyl)-5-methyl-4,5-dihydro-1,3,4-oxadiazol-2-yl)methylthio)-3-o- tolylquinazolin-4(3H)-one (PD I-D ) in CF and DMF were investigated at 303, 308 and 313 K and at atmospheric pres- sure. Using ρ, η and U data various acoustical and thermodynamic parameters such as acoustical impendence (Z), isentropic compressibility (κ S ), intermolecular free path length (L f ), Rao's molar sound function (R m ), Van der Waals constant (b), internal pressure (π), relaxation time (τ), free volume (V f ) and solvation number (S n ) were cal- culated and fairly good co-relationship between calculated parameters were obtained. A fairly good to excellent cor- relation between a given parameter and concentration is observed at all temperatures and solvent systems studied. Linear or non-linear increases or decreases of acoustical parameters with concentration and temperature indicated the existence of strong molecular interactions between studied systems. Moreover, the experimental results for the pure solvents and solutions of compound PD I-D studied has been carried out to analyze carefully how the structural modifications affect the values of Gibbs energy of activation (ΔG*), enthalpy of activation (ΔH*) and entropy of ac- tivation (ΔS*) in CF and DMF. © 2013 Elsevier B.V. All rights reserved. 1. Introduction A literature survey reveals that ultrasound radiations are used in synthetic organic chemistry, which causes a decrease of reaction time, increase of yield, lower reaction temperature, avoidance of phase transfer catalysis etc. [1–6]. Further, ultrasonic velocity mea- surements have been used to study the nature of molecular interac- tions in various binary [7–10] and ternary liquid mixtures. Much of work has been done in solutions of polymers [11–13], pharma mate- rials [14,15], amino acids [16] and other electrolytes [17–19] and non-electrolytes [20,21]. This technique has been utilized by many re- searchers for solution studies of organic compounds [22–27]. Litera- ture survey shows that the synthesis of 1,3,4-oxadiazole was carried out by a number of workers [28,29] because of its biological activities such as antimalarial, antifungal [30] and antibacterial activities. The choice of 1,3,4-oxadiazole is due to its multi-applicability in the field of medicine. It is an important moiety in the drug industry. The applications of these compounds attract us to study their behav- iors in various solvents and also investigate their thermodynamic and chemical kinetic parameters. In this context, the present paper, we have used this ultrasonic technique for the better understanding of the molecular interactions in solution and acoustical properties of newly synthesized 1,3,4-oxadiazole derivative (compound PD I-D ). CF and DMF were used as solvents for comparison of these properties. The study was also carried out at three different temperatures 303, 308 and 313 K over a wide range of concentrations (0.01 M to 0.001 M). The experimental data is used for the evaluation of various thermodynamic and acoustical parameters by which molecular inter- actions in solutions are interpreted. 2. Experimental 2.1. Materials The 1,3,4-oxadiazole derivative of 2-((4-acetyl-5-(4-bromophenyl)- 5 - methyl - 4, 5 - dihydro -1, 3, 4 - oxadiazol -2-yl)methylthio) - 3 - o - tolylquinazolin-4(3H)-one (PD I-D ) used in this study was synthesized in our laboratory [31]. The molecular weight of compound PD I-D is 563.47 g∙mol −1 . The structural formula of synthesized compound PD I-D is shown in Fig. 1. The solvents: Chloroform (Prod. no. 010333) and N,N-dimeth- ylformamide (Prod. no. 010445) used in the present study were of A R grade and supplied by Spectrochem Pvt. Ltd. (Mumbai), with a purity of 0.99–0.994 mole fraction and 0.995 mole fraction (by gas chromatographic analysis values provided by the manufacturer). The solvents were purified according to literature methods [32]. The final purities of the solvents were also confirmed by Perkin Elmer 8410 gas chromatograph equipped with 60/80 carbosieve S-II packed column (5 ft long, 0.125 mm i.d.). The flow rate of N 2 was maintained at 50 mL/min N 2 and, initial column temperature was kept at 125 °C, Journal of Molecular Liquids 180 (2013) 179–186 ⁎ Corresponding author. Tel.: + 91 2782439852 (office), + 91 9687615488 (mobile). E-mail address: drgodhani@yahoo.com (D.R. Godhani). 0167-7322/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.molliq.2013.01.017 Contents lists available at SciVerse ScienceDirect Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq