Sujjad Hyder

Volumetric, viscometric and refractive index study of amino acids in mixed solvents at 308.15 K

Densities, ρ, viscosities, η and refractive indices n D for solutions of (0.10, 0.20, 0.30, 0.40 and 0.50 M) glycine (Gly), DL-alanine (Ala) and L-serine (Ser) in aqueous 1-propanol (10 and 30% v/v) at 308.15 K have been determined. These data have been used to calculate apparent molar volumes, φv, partial molar volumes, and Falkenhagen and Jones–Dole coefficients, A and B, respectively. Free energies of activation of viscous flow, and per mole of solvent and solute, respectively, were obtained by using transition state theory to the B-coefficient data. The molar refractive indices, R D were calculated from the experimental values of refractive indices for all the three amino acids + aqueous 1-propanol ternary mixtures. These parameters were used to discuss the solute–solute and solute–solvent interactions and also the effect of cosolvent (1-propanol) on these interactions.

Volumetric and Refractive Index Behaviour of α-Amino Acids in Aqueous CTAB at Different Temperatures

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 cetyltrimethylammonium bromide (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 (ϕv0), at infinite dilution and partial molar volumes of transfer ϕv0(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 ϕv0 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 (NH3+, 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 cetyltrimethylammonium cation on these interactions.