Abstract: Densities (ρ) and refractive indices (nD) of glycine (Gly), DL-alanine (Ala), DL-valine (Val) (0.02, 0.04, 0.06, 0.08, and 0.10 mol·L-1) in 0.005 and 0.008 mol·L-1 aqueous cetyltrimethylammoniumbromide (CTAB) have been measured at 298.15, 303.15, 308.15, and 313.15 K. The density data have been utilized to calculate apparent molar volumes (φv), partial molar volumes (φ0v), at infinite dilution and partial molar volumes of transfer φ0v(tr) of amino acids. The refractive index data have been used to calculate molar refractivity (RD) of amino acids in aqueous cetyltrimethylammonium bromide. It has been observed that φ0v varies linearly with increasing number of carbon atoms in the alkyl chain of amino acids, and hence, was split to get contributions from the zwitterionic end groups (NH+3, COO-) and methylene group (CH2) of the amino acids. The behaviour of these parameters has been used to investigate the solute-solute, solute-solvent interactions and the effect of cetyltrimethylammoniumcation on these interactions.

Key words: Amino acid, Cetyltrimethylammonium bromide, Partial molar volume, Refractive index, Solute-solute and solute-solvent interactions