Carmen M. Romero

Effect of temperature on partial molar volumes and viscosities of aqueous solutions of α-dl-Aminobutyric acid, dl-Norvaline and dl-Norleucine

In this work, we present experimental results for partial molar volumes and viscosities of aqueous solutions of α-dl-aminobutyric acid, dl-norvaline and dl-norleucine at 288.15, 293.15, 298.15 and 303.15 K. The thermodynamic behavior of aqueous amino acid solutions is compared with that reported for glycine and α-alanine in water and is discussed in terms of group additivity and electrostriction. The temperature dependence of the infinite dilution partial molar volumes and the B viscosity coefficients are interpreted in terms of amino acid hydration. According to the usual hydrophobicity criteria, the amino acids considered do not have a hydrophobic character and their behavior is dominated by the polar groups.

Apparent molal volumes and viscosities of dl-α-alanine in water–alcohol mixtures

Abstract A systematic study of the experimental behavior of apparent molal volumes and viscosities of dl -α-alanine in aqueous 1-propanol, 1-butanol and 1,2-propanediol mixtures at 25°C is presented. The concentrations of the alcohol–water mixtures used as solvents were selected taking into account their special thermodynamic behavior and in particular the abrupt change observed in the dependence of partial molal volumes with concentration. The results are discussed in terms of changes in solvent structure.

Surface tension of aqueous solutions of alcohol and polyols at 298.15 K

Surface tension of aqueous solutions of 1-propanol (nP), 1,2-propanediol (12PD), 1,3-propanediol (13PD) and 1,2,3-propanetriol (123PT) were measured using the method of capillary rise as a function of concentration at 298.15 K with emphasis in the very dilute region. The decrease of surface tension with mole fraction of alcohol becomes less pronounced as the number of OH groups increases. The surface enrichment effect, reflected by the slopes for the curves of surface tension versus composition, is correlated with the number of hydroxyl groups in the solute and the hydrophilic character of the solutes.

Thermodynamic properties of aqueous alcohol and polyol solutions

In this work, we present experimental results for partial molar volumes and viscosities of aqueous solutions of n-propanol, 1,2-propanediol, 1,3-propanediol and 1,2,3-propanetriol at 25.00°C and literature data for other systems. The thermodynamic behavior of aqueous alcohol and polyol solutions is discussed in terms of the relationship between polar and non-polar groups and their effect on water structure. The relationship of hydroxyl groups to the number of non-polar groups in the solute determines the balance between hydrophobic and hydrophilic interactions and as a direct consequence, the thermodynamic behavior of properties such as partial molar volumes, and viscosity.

Apparent Molar Volumes of Amino Acids in Very Dilute Aqueous Solutions at 25,00°C

Abstract The apparent molar volumes of DL–α–alanine, DL–β–alanine, DL–α–aminobutyric acid, DL–α–phenylalanine, DL–serine and DL–aspartic acid in very dilute aqueous solutions at 25,00°C were determined from density measurements. From these data it is shown that the concentration dependence of the apparent molar volume of these amino acids at very low molality differs from the behavior found at concentrations higher than 0,01m. This change has been attributed to solute-water interactions which prevail at very high dilution.

Effect of temperature on partial molar volumes and viscosities of dilute aqueous solutions of 1-butanol, 1,2-butanediol, 1,4-butanediol, 1,2,4-butanetriol, and butanetetrol

Experimental densities and viscosities of dilute aqueous binary mixtures of 1-butanol, 1,2-butanediol, 1,4-butanediol, 1,2,4-butanetriol, and 1,2,3,4-butanetetrol (erythritol) were measured in the temperature range from 283.15 to 323.15 K. Apparent molar volumes were determined as a function of composition from density measurements. The limiting partial molar volumes of alcohols in aqueous solution were evaluated through extrapolation. The relative viscosity values were adjusted by least-squares to a second order equation to obtain the viscosity B coefficient which has been related to the size and shape of the solute molecule. The temperature dependence of the partial molar volume at infinite dilution and the viscosity B coefficient are discussed in terms of the relationship among polar and non polar groups on water structure and the effect of the position of hydroxyl groups in the molecule.

Apparent Molar Volumes and Viscosities of Dl-α-Alanine in Water-Ethanol Mixtures

Abstract In this work we present a systematic study of the apparent molar volumes and the viscosities of DL-α-alanine in aqueous ethanol solutions at 25,00°C. The molar fractions of ethanol for the solvent mixtures were selected taking into account that thermodynamic properties such as partial molar volumes and heat capacities of these mixtures show a transition concentration around X et = 0,1 at which its behavior suffers a deep change. Besides, this ethanol concentration is near to that required to produce 50% of protein denaturation. The results were used to evaluate the limiting partial molar volume V0 of the solute the volume changes associated with its transfer from water to aqueous ethanol solutions and the viscosity B coefficients of DL-α-alanine. The values obtained for the transference molar volumes and the viscosity B coefficients of alanine in the aqueous mixtures show a minimum at X et = 0,1000. The results are discussed in terms of changes in the solvent structure (Ref. [1])

Limiting values of diffusion coefficients of glycine, alanine,

Abstract.The side chain effect on transport in ionic aqueous salt solutions was investigated for

\alpha

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-amino butyric acid, norvaline and norleucine in a relevant physiological aqueous medium

α-amino acids glycine, alanine,