The speed of sound and density of acetophenone, propiophenone, para-methyl acetophenone, and para-chloro acetophenone with acetonitrile have been measured over the entire range of mole fraction at T=308.15 K. From the experimentally determined data, values of deviations in speed of sound, isentropic compressibility, and intermolecular free-length have been computed. The deviation in isentropic compressibility Delta kappa(S) is fitted to a Redlich-Kister type equation. The deviation in speed of sound is positive where as the deviations in isentropic compressibility and intermolecular free length are negative for all the systems. This trend indicates that the specific interactions are operative between unlike molecules. The reactivity order of ketones with acetonitrile is para-chloro acetophenone > paramethyl acetophenone > acetophenone > propiophenone. (c) 2006 Elsevier Ltd. All rights reserved.