A systematic thermo-physical characterization of the two compounds 2-((4-acetyl-5-(4-methoxyphenyl)-5-methyl-4,5-dihydro-1,3,4-oxadiazol-2-yl) methylthio)-3-o-tolylquinazolin-4(3H)-one (PDI-A) and 2-((4-acetyl-5-methyl-5-p-tolyl-4,5-dihydro-1,3,4-oxadiazol-2-yl) methylthio)-3-o-tolylquinazolin-4( 3H)-one (PDI-G) in two different solvents viz. chloroform (CF) and N,N-dimethylformamide (DMF) were elucidated. Thus, density (rho), viscosity (eta) and ultrasonic sound velocity (U) and thereby various acoustical and thermodynamic parameters have been determined over the range of T = (303, 308, and 313) K and at atmospheric pressure. Moreover, a comparison between experimental results for the pure solvents and solutions of compound PDI-A and compound PDI-G studied has been carried out to analyze carefully how the structural modifications affect the values of Gibbs energy of activation (Delta G), enthalpy of activation (Delta H) and entropy of activation (Delta S) in CF and DMF. (C) 2012 Elsevier Ltd. All rights reserved.