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Journal of Structural Chemistry

2011 year, number 1

VOLUME PROPERTIES OF A TERNARY SYSTEM: WATER-UREA-AMINO ACID. DILUTE AND CONCENTRATED SOLUTIONS

V. P. Korolev
Keywords: urea, amino acid, aqueous solutions, partial volumes
Pages: 101-109

Abstract

Partial molar volumes  of amino acids in an aqueous urea solution are studied. For a saturated urea solution  equals the molar volume of the amino acid, therefore, in the saturated solution, the amino acid dissolves without changing the system volume. Hydrophobic effects are manifested in the volumetric characteristics only in dilute (<1 mol/kg) urea solutions. Within a three-layer hydration model, the numbers of amino acid hydration are found. By the example of alanine and leucine, it is shown that their decrease with increasing urea concentration is determined by a zwitterionic moiety and does not depend on the size of the hydrocarbon radical of the amino acid.