Solvent Effects on the Protonation Constants of Some alpha-Amino Acid Esters in 1,4-Dioxane-Water Mixtures


Dogan A. , Aslan N., CANEL E., KILIÇ E.

JOURNAL OF SOLUTION CHEMISTRY, vol.39, no.11, pp.1589-1596, 2010 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 39 Issue: 11
  • Publication Date: 2010
  • Doi Number: 10.1007/s10953-010-9612-z
  • Title of Journal : JOURNAL OF SOLUTION CHEMISTRY
  • Page Numbers: pp.1589-1596

Abstract

The stoichiometric protonation constants of some alpha-amino acid esters (glycine methyl ester, glycine t-butyl ester, l-valine methyl ester, l-valine ethyl ester, l-valine t-butyl ester, l-serine methyl ester, l-serine ethyl ester, l-leucine methyl ester, l-leucine ethyl ester, l-leucine t-butyl ester, l-alanine methyl ester, l-alanine benzyl ester, l-phenylalanine methyl ester, l-phenylalanine ethyl ester, and l-phenylalanine t-butyl ester) in water and 20%, 40%, and 60% (v/v) 1,4-dioxane-water mixtures have been determined at an ionic strength of 0.10 mola <...L-1 NaCl and at 25.0 +/- 0.1 A degrees C under a nitrogen atmosphere. A potentiometric method was used and the calculation of the protonation constants has been carried out using the BEST computer program. The results were discussed in terms of macroscopic properties of the mixed solvent. The stoichiometric protonation constants were influenced by changes in solvent composition and their variations were discussed in terms of preferential solvation. Also, knowledge the protonation constant of alpha-amino acid esters will be helpful when determining the microscopic equilibrium constants of their corresponding amino acids.