Ionic liquid 1-methyl-3-pentylimidazolium bromide have been synthesised and confirmed by characterisation techniques H-1 NMR, C-13 NMR, MASS and IR spectroscopy. Density and speed of sound of aqueous amino acids (L-cysteine and N-acetyl-L-cysteine) in aqueous ionic liquid (0.005, 0.01, 0.03, 0.05) mol.kg(-1) as solvent have been determined at four different temperatures T = (288.15, 298.15, 308.15, 318.15) K. Using these experimental data apparent molar volumes (V-phi), limiting apparent molar volume (V degrees(phi)), experimental slope (S-v), standard partial molar volumes of transfer (Delta V-phi(0)), Limiting apparent molar expansibilities (E degrees(phi)), apparent molar isentropic compression (K-phi,K-s), limiting apparent molar isentropic compression (K-phi(0),(s)) and standard partial molar isentropic compression of transfer (Delta K-phi(0),(s)) have been evaluated. The pair and triplet interaction coefficient have also been calculated. The values of these parameters are helpful for interpretation in terms of solute-solute and solute-solvent interactions, ion hydrophilic, hydrophilic-hydrophilic and hydrophilic-hydrophobic interactions in the amino acid and ionic liquid solutions. The structure making or structure-breaking tendency of amino acids has also been studied using these thermodynamic parameters. (C) 2017 Elsevier Ltd.