Physicochemical and friccohesity study of glycine, l-alanine and l-phenylalanine with aqueous methyltrioctylammonium and cetylpyridinium chloride from T = (293.15 to 308.15) K

• Surface tensions are as water > aq.CPC > aq.MTOAC.
• Positive Vϕ0 inferred stronger solute–solvent interactions.
• Glycine and l-phenylalanine transfer volumes are positive.
• κs,ϕ0 of glycine and l-phenylalanine with surfactants > with water.
• Weaker electrostriction produced positive Δκs,ϕ0 for glycine and l-phenylalanine.

Density ρρ, sound velocity u, viscosity η, apparent molar volume Vϕ  , isentropic compressibility κsκs, and apparent molar isentropic compressibility κs,ϕκs,ϕ of glycine, l-alanine and l-phenylalanine: (0.05 to 0.15 mol · kg−1) with water, 0.002 mol · kg−1 aqueous methyltrioctylammonium chloride (MTOAC) and cetylpyridinium chloride (CPC) are reported at T = (293.15, 298.15, 303.15 and 308.15) K. The data were regressed against composition and regression constants: apparent molar volume at infinite dilution Vϕ0, apparent molar isentropic compressibility at infinite dilution κs,ϕ0 and viscosity B-coefficient are studied. Surface tension γ and friccohesity σ   data were calculated from density, pendant drop number and viscous flow time. The Vϕ0 values are found as Vϕ(gly,l-phalwithwater)0 < Vϕ(gly,l-phalwithsurfactatnt)0, Vϕ(l-alawithsurfactatnt)0 < Vϕ(l-alawithwater)0 and κs,ϕ0 values as κϕ(gly,l-phalwithwater)0 < κϕ(gly,l-phalwithsurfactatnt)0, κϕ(l-alawithsurfactatnt)0 < κϕ(l-alawithwater)0. Surface tension of the solvents are found as water > CPC > MTOAC. Amino acids with surfactants have produced higher friccohesity than with water whereas the friccohesityof amino acids with water and surfactants is found as l-phal > l-Ala > gly over the entire temperature range but with CPC at T = 298.15 K, the order is l-phal > gly > l-Ala. The variations in physicochemical data with temperature and composition inferred structural changes with stronger solute–solvent interactions.

Figure depicts response of amino acids towards cationic surfactants in aqueous solution at constant temperatures. Apparent isentropic compressibilities at infinite dilution (κs,ϕ0/1012 m5 · N−1 · mol−1) for amino acids are as l-Ala < Gly < l-phal with stronger interaction of l-phal with surfactants. This infers a role of pi-conjugation on amino acid-surfactants interactions at variable temperatures. Gly and l-phal show similar interaction trend with increase in temperature whereas for l-Ala is just opposite.Figure optionsDownload as PowerPoint slide