I. A. Skvortsov

Thermodynamic characteristics of stepwise dissociation of glycyl-glycyl-glycine in aqueous solutions

The heats of interaction between glycyl-glycyl-glycine and solutions of nitric acid and potassium hydroxide are determined by calorimetry at 298.15 K and ionic strengths of 0.25, 0.50, and 0.75 in the presence of KNO3. The standard thermodynamic characteristics (ΔrH°, ΔrG°, and ΔrS°) of acid–base interaction in aqueous solutions of the peptide are calculated. The effect of background electrolyte concentration on the enthalpy of dissociation of glycyl-glycyl-glycine is discussed.

Thermochemical study of the reactions of acid–base interaction in an aqueous solution of α-aminobutyric acid

The heat effects of the interaction between a solution of α-aminobutyric acid and solutions of HNO3 and KОН are measured by means of calorimetry in different ranges of рН at 298.15 K and values of ionic strength of 0.25, 0.5, and 0.75 (KNO3). The heat effects of the stepwise dissociation of the amino acid are determined. Standard thermodynamic characteristics (ΔrH0, ΔrG0, and ΔrS0) of the reactions of acid–base interaction in aqueous solutions of α-aminobutyric acid are calculated. The connection between the thermodynamic characteristics of the dissociation of the amino acid and the structure of this compound is considered.

Thermodynamics of the dissolution of crystalline L-methionine in water

The enthalpies of dissolution of crystalline L-methionine in water and aqueous solutions of potasium hydroxide at 298.15 K are measured by means of direct calorimetry. The standard enthalpies of formation are calculated for L-methionine and products of its dissociation in aqueous solution.

Thermodynamic characteristics of acid-base equilibria of DL-α-alanyl-DL-norleucine in aqueous solutions at 298 K

Protolytic equilibria in aqueous solutions of DL-α-alanyl-DL-norleucine are studied via potentiometry and calorimetry. Measurements are made at 298.15 K and ionic strengths of 0.5, 1.0, and 1.5 (against a background of potassium nitrate). The thermodynamic characteristics (pK, ΔG, ΔH, ΔS) of the stepwise dissociation of the dipeptide both in aqueous-salt solutions and in standard solution are obtained for the first time.

Enthalpies of Dissolution of Crystalline Naproxen Sodium in Water and Potassium Hydroxide Aqueous Solutions at 298 K

The enthalpies of dissolution of crystalline naproxen sodium in water and aqueous solutions of KOH at 298.15 K are measured by direct calorimetric means in a wide range of concentrations. The acid–base properties of naproxen sodium at ionic strength I ~ 0 and I = 0.1 (KNO3) and a temperature of 298.15 K are studied by spectrophotometric means. The concentration and thermodynamic dissociation constants are determined. The standard enthalpies of the formation of naproxen sodium and the products of its dissociation in aqueous solution are calculated.

Thermodynamics of Dissolution for Crystalline Racemic Tartaric and Glutaric Acids and Isatin in KOH Aqueous Solutions at 298.15 K

Enthalpies of dissolution are found for crystalline racemic tartaric and glutaric acids and isatin in water and in potassium hydroxide solutions at 298.15 K via direct calorimetry. The protolytic equilibria in isatin aqueous solutions are studied at 298.15 K and ionic strengths of 0.5 (relative to potassium nitrate) by potentiometric means. Standard enthalpies of formation are calculated for racemic tartaric and glutaric acids, isatin, and the products of their dissociation in aqueous solutions.

Thermodynamics of reactions of complex formation for Ce3+ and Er3+ ions with glycine in an aqueous solution

Enthalpies of complex formation for glycine (HL±) with Ce3+ and Er3+ ions at 298.15 K and the value of the ionic strength of 0.5 (KNO3) are determined by calorimetric means using two independent procedures. Thermodynamic characteristics of the reactions of formation for complexes of glycine with Ce3+ and Er3+ ions at various [metal]: [ligand] molar ratios are calculated.

Thermochemical Study of Acid—Base Reactions in a Glycyl-Tyrosine Aqueous Solution

Thermal effects of the interaction between a glycyl-tyrosine solution and solutions of HNO3 and KOH in different pH ranges at a temperature of 298.15 K and ionic strengths of 0.25, 0.5, and 0.75 (KNO3) are measured via calorimetry. Thermal effects of the stepwise dissociation of the dipeptide are determined. Standard thermodynamic characteristics ΔrH°, ΔrG°, and ΔrS° of acid—base reactions in aqueous solutions of glycyl-tyrosine are calculated. The relationship between the thermodynamic characteristics of dipeptide dissociation and the structure of this compound is examined.

Standard enthalpies of formation for crystalline serine and isoserine and products of their dissociation in aqueous solutions

The heats of solution of crystalline serine and isoserine in water and potassium hydroxide solutions are measured via direct calorimetry at 298.15 K. The standard enthalpies of formations of amino acids and products of their dissociation in aqueous solution are calculated.

Standard enthalpies of formation of γ-aminobutyric acid and the products of its dissociation in aqueous solution

Heat effects of the dissolution of crystalline γ-aminobutyric acid in water and potassium hydroxide solutions are determined by direct colorimetry at 298.15 K. Standard enthalpies of formation of γ-aminobutyric acid and the products of its dissociation in aqueous solution are calculated.