Effect of temperature on viscosity properties of some alpha-amino acids in aqueous urea solutions.
Viscosities for solutions of glycine, DL-alpha-alanine, DL-alpha-amino-n-butyric acid, DL-valine, DL-leucine and L-serine in 5 mol kg(-1) aqueous urea have been determined at 278.15, 288.15, 298.15 and 308.15 K. The viscosity B-coefficients for the amino acids in the aqueous urea solution have been calculated at different temperatures. The effect of temperature on the B-coefficients is discussed on the basis of the Feakins equation. The contribution of solute to the activation parameters (delta mu0*2, deltaH0*2, deltaS0*2) for viscous flow of the solution have been calculated, together with the Gibbs energy, enthalpy and entropy of transfer for the amino acids from the ground-state solvent to the hypothetical viscous transition state solvent. The contributions of the charged end group (NH3+, COO-) and CH2 groups of the amino acids to B-coefficient and delta mu0*2 have been also estimated using the linear correlations between B-coefficient or delta mu0*2 and the number of carbon atoms in the alkyl chains of the amino acids. All the activation parameters are discussed in terms of the solute-solvent interactions in the ground and transition states.
Wang
J
J
Department of Chemistry, Henan Normal University, Xinxiang, PR China. jwang@mail.henannu.edu.cn
Yan
Z
Z
Zhang
H
H
Lu
J
J
D000596:Amino Acids / Q000737:chemistry*; D012996:Solutions; D013696:Temperature; D013816:Thermodynamics; D014508:Urea; D014783:Viscosity; D014867:Water
D000596:Amino Acids; D012996:Solutions; D014867:Water; D014508:Urea