ABSTRACT The pseudo-Gruneisen parameter , effective Debye temperature, acoustic nonlinearity parameter , internal pressure and isobaric thermal expansion coefficient have been evaluated for binary liquid mixtures of formamide (FA) and N-methylformamide (NMF) with 2-chloroethanol (2Cl-OH) at 298.15 K, 308.15 K and 318.15 K, over the entire concentration range. The excess pseudo-Gruneisen parameter , excess effective Debye temperature , excess nonlinearity parameter, excess internal pressure and excess isobaric thermal expansion coefficient were also calculated. The calculated values are reasonably satisfactory with the experimental results on sound propagation data of liquid mixtures. These physicochemical parameters play an important role in understanding of the significance of anharmonic and nonlinear behaviour with regard to intermolecular interactions in the liquid mixtures.