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Volumetric Investigations on Molecular Interactions of Glycine/l-alanine in Aqueous Citric Acid Solutions at Different Temperatures.

Poonam PatyarGurpreet KaurTarnveer Kaur
Published in: Journal of solution chemistry (2018)
Apparent molar volumes ( ϕ V ) of glycine/l-alanine in water and in aqueous citric acid (CA) solutions of varying concentrations, i.e. (0.05, 0.10, 0.20, 0.30, 0.40 and 0.50) mol·kg-1 were determined from density measurements at temperatures T = (288.15, 298.15, 308.15, 310.15 and 318.15) K and at atmospheric pressure. Limiting partial molar volumes ( ϕ V o ) and their corresponding partial molar volumes of transfer ( Δ tr ϕ V ) have been calculated from the ϕ V data. The negative Δ tr ϕ V values obtained for glycine/l-alanine from water to aqueous CA solutions indicate the dominance of hydrophilic-hydrophobic/hydrophobic-hydrophilic and hydrophobic-hydrophobic interactions over ion/hydrophilic-dipolar interactions. Further, pair and triplet interaction coefficients, i.e. ( V AB ) and ( V ABB ) along with hydration number ( n H ) have also been calculated. The effect of temperature on the volumetric properties of glycine/l-alanine in water and in aqueous CA solutions has been determined from the limiting partial molar expansibilities ( ∂ ϕ V o / ∂ T ) p and their second-order derivative ( ∂ 2 ϕ V o / ∂ T 2 ) P . The apparent specific volumes ( ν ϕ ) for glycine and l-alanine tend to approach sweet taste behavior both in the presence of water and in aqueous CA solutions. The ν ϕ values for glycine/l-alanine increase with increase in concentration of CA at all temperatures studied. This reveals that CA helps in enhancing the sweet taste behavior of glycine/l-alanine which also supports the dominance of hydrophobic-hydrophobic interactions.
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