The acoustic nonlinearity parameter (B/A) and associated thermophysical properties of solvent systems comprising N-ethyl-2-pyrrolidone with ethanolamine, diethanolamine, and triethanolamine were investigated over the entire concentration range and temperatures 293.15–323.15 K. The previously reported density and ultrasonic velocity data from Blanco et al. [9] were theoretically re-analyzed using several empirical and semi-empirical acoustic nonlinearity models. The isobaric temperature coefficients \(\:{\left(\partial\:u/\partial\:T\right)}_{P}\) and isothermal pressure coefficients of ultrasound speed \(\:{\left(\partial\:u/\partial\:P\right)}_{T}\) were also determined to examine molecular interactions. Variations in acoustic and excess non-linearity parameters indicate strong specific interactions, mainly hydrogen bonding between the -C = O- group of N-ethyl-2-pyrrolidone and -OH groups of alkanolamines, along with steric effects due to increasing substitution. Increasing temperature weakens associative interactions. The results suggest that nonlinear acoustic analysis can complement conventional thermodynamic approaches in understanding molecular association in strongly interacting liquid mixtures.
