THERMODYNAMIC CHARACTERISTICS OF COMPLEXATION OF NICKEL (II) WITH L-TYROSINE AND SOLVATION OF REAGENTS in AQUEOUS ...

DOI: 
10.6060/tcct.20165910.5401

Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2016. V. 59. N 10. P. 24-29

THERMODYNAMIC CHARACTERISTICS OF COMPLEXATION OF NICKEL (II) WITH
L-TYROSINE AND SOLVATION OF REAGENTS IN AQUEOUS SOLUTIONS OF ETHANOL

By means of calorimetric titration the enthalpies of complex formation of nickel (II) with L-tyrosine in solvents containing 0 – 0.6 molar fractions of ethanol were determined at the temperature of 273 K and ion force of solution of 0. Initial solutions were L-tyrosinate of sodium and nickel perchlorate of analytical grade. Molar enthalpies were calculated taking into account the fraction distribution of formed complexes, their stability constants and dilu-tion enthalpies of titrant. Stepwise stability constants of complexes of L-tyrosine with nickel (II) which are necessary to know for enthalpies calculations were determined by the method of potentiometric titration. The probable scheme of stepwise reactions of complex formation is discussed. Changes in entropy of reactions as well as the transfer enthalpies of all reagents from water in aqueous ethanol have been calculated. It has been established, that effect of solvent on the thermodynamic characteristics of complexation depends considerably on a solvation of ligand, i.e. anion of tyrosine.

Key words: L-tyrosine, amino acids, complex compounds, complexation, enthalpy, calorimetry, solvation, binary solvents

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2016, Т. 59, № 10, Стр. 24-29

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