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Title: Studies on complexation between urea and 18-crown-6 in aqueous solutions at 298.15K
Authors: Tomar, Preeti
Keywords: Solution chemistry;Complexation;Urea;Crown ethers
Issue Date: Sep-2009
Publisher: CSIR
Abstract:  Osmotic vapor pressure and density measurements have been made for binary aqueous urea solutions (0.1m-1m) and ternary aqueous solutions containing three different concentrations of 18-crown-6 (0.1, 0.2 and 0.5m) at 298.15K. The molal activity coefficients of urea, water and 18-crown-6 in binary as well as in ternary solutions have been calculated. Thermodynamic equilibrium constant, salting coefficient and molecular interaction parameters have been determined. The results are explained in terms of 1:4 stoichiometric complex formation with urea at the lowest concentration of 18-crown-6 having a small equilibrium constant value. At higher 18-crown-6 concentrations, water forms hydrogen bond with crown ring oxygen atoms and hydrophobic interaction between 18-crown-6 molecules outweighs the interaction of urea with 18-crown-6 molecules, resulting in salting out of urea molecules.
Page(s): 1247-1250
ISSN: 0975-0975(Online); 0376-4710(Print)
Appears in Collections:IJC-A Vol.48A(09) [September 2009]

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