Physical properties such as densities and speeds of sound of 1-hexyl-3-methylimmidazolium based room temperature ionic liquids (RTILs); with bromide (Br), tetrafluoroborate (BF4), hexafluorophosphate (PF6), as anions in ethylene glycol monomethyl ether (EGMME), over the whole composition range were measured at T = (288.15-318.15) K and at atmospheric pressure. Experimental densities were used to obtain excess molar volumes, V-E. The V-E values for each of the mixture studied were negative and decreased with increase in temperature with the following order: [PF6] > [BF4]> [Br]. Deviations in isentropic compressibility, Delta kappa(S) were calculated from the experimental speeds of sound and densities. The Delta kappa(S) values were negative over the entire range of composition for all mixtures with the exception of ILs containing [Br] and [BF4] anions, which changes sign from negative to positive at low temperatures. Both V-E and Delta kappa(S) were fitted to the Redlich-Kister polynomial equation to obtain the binary coefficients and the standard errors. The molecular scale interactions between (ILs) and EGMME were investigated through H-1 NMR spectroscopy. NMR chemical shifts for various protons of (ILs) or EGMME molecules and their deviations show hydrogen bonding interactions of varying strengths between (ILs) and EGMME in their binary mixtures. (C) 2012 Elsevier B.V. All rights reserved.