Abstract
The acid-base equilibria of glycine have been studied in different aqueous solutions of methanol and ethanol (0–45 % v/v) using a potentiometric method. In this study, the macro and micro protonation constants of the amino acid and its tautomeric constant have been determined at 25 °C and constant ionic strength (0.1 mol⋅dm−3 NaClO4). The protonation and the tautomeric constants of glycine in different binary mixtures were analyzed in terms of the Kamlet, Abboud and Taft (KAT) parameters. Single-parameter correlations of the constants versus α (hydrogen-bond donor acidity), β (hydrogen-bond acceptor basicity) and π ∗ (dipolarity/polarizability) are poor in all solutions. Multi-parameter correlations show better results, but dual-parameter correlations represent significant improvements with regard to the single- and multi-parameter models. Linear correlation is observed when the experimental protonation constant values are plotted versus the calculated ones when the KAT parameters are considered. Finally, the results are discussed in terms of the effect of the solvent on protonation and tautomeric constants.
Similar content being viewed by others
References
Noszal, B., Rabenstein, D.L.: Nitrogen-protonation microequilibria and C(2)-deprotonation microkinetics of histidine, histamine, and related compounds. J. Phys. Chem. 95, 4761–4765 (1991)
Boros, M., Kokosi, J., Vamos, J., Noszal, B.: Complete resolution of the microscopic protonation equilibria of N-methyl-D-aspartic acid and related compounds. J. Pharm. Biomed. Anal. 43, 1306–1314 (2007)
D’Angelo, J.C., Collette, T.W.: A method for the measurement of site-specific tautomeric and zwitterionic microspecies equilibrium constants. Anal. Chem. 69, 1642–1650 (1997)
Noszal, B., Szakacs, Z.: Microscopic protonation equilibria of oxidized glutathione. J. Phys. Chem. 107, 5074–5080 (2003)
Zapala, L., Kalembkiewicz, J., Sitarz-Palczak, E.: Studies on equilibrium anthranilic acid in aqueous solutions and in two-phase systems: aromatic solvent–water. Biophys. Chem. 140, 91–98 (2009)
Dogan, A., Kilic, E.: Tautomeric and microscopic protonation equilibria of some α-amino acids. Anal. Biochem. 365, 7–13 (2007)
Reichardt, C.: Solvents and Solvent Effects in Organic Chemistry, 3rd edn. VCH, New York (2004)
Staszak, Z., Bartecki, A.: Influence of the bulk and donor-acceptor properties of solvent on ligand field spectra. Spectrosc. Lett. 22, 1193–1201 (1989)
Gharib, F., Jabbari, M., Farajtabar, A., Shamel, A.: Solvent effects on protonation and complexation of glutamic and aspartic acids with molybdenum(VI) in different solutions of methanol. J. Chem. Eng. Data 53, 1772–1778 (2008)
Gharib, F.: Solvent effects on protonation and complexation of penicillamine and thallium(I) in different aqueous solutions of methanol. J. Chem. Eng. Data 55, 1547–1553 (2010)
Farajtabar, A., Gharib, F.: Solvent effect on protonation constants of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin in different aqueous solutions of methanol and ethanol. J. Solution Chem. 39, 231–244 (2010)
Gharib, F., Sadeghi, F.: Solvent effects on complexation of thallium(I) with guanosine 5′-monophosphate in methanol–water mixtures. Appl. Organomet. Chem. 21, 218–225 (2007)
Jabbari, M., Gharib, F., Mohammadpour Amini, M., Azadmehr, A.: Hydrolysis of dimethylphenyltin(IV) and triphenyltin(IV) chlorides in different aqueous ethanol solutions. Can. J. Chem. 86, 751–756 (2008)
Shamel, A., Jaberi, F., Gharib, F.: Protonation constants of adenine and adenosine in different aqueous solutions of methanol and ethanol. J. Chem. Eng. Data 55, 5176–5181 (2010)
Gharib, F., Farajtabar, A., Masteri Farahani, A., Bahmani, F.: Solvent effects on protonation constants of tryptophan in some aqueous aliphatic alcohol solutions. J. Chem. Eng. Data 55, 327–332 (2010)
Benesch, R.E., Benesch, R.: The acid strength of the –SH group in cysteine and related compounds. J. Am. Chem. Soc. 77, 5877–5881 (1955)
Martell, A.E., Motekaitis, R.J.: The Determination and Use of Stability Constants. VCH, Weinheim (1988)
Edsall, J.T., Blanchard, M.H.: The activity ratio of zwitterions and uncharged molecules in ampholyte solutions: the dissociation constants of amino acid esters. J. Am. Chem. Soc. 59, 2337–2353 (1933)
Maleki, N., Haghighi, B., Safavi, A.: Evaluation of formation constants, molar absorptivities of metal complexes, and protonation constants of acids by nonlinear curve fitting using Microsoft Excel Solver. Microchem. J. 62, 229–236 (1999)
Rossotti, A.: The Study of Ionic Equilibria. Longman, New York (1978)
Koseoglu, F., Kilic, E., Dogan, A.: Studies on protonation constants and solvation of some α-amino acids in dioxan–water mixtures. Anal. Biochem. 277, 243–246 (2000)
Dogan, A., Koseoglu, F., Kilic, E.: Studies on macroscopic protonation constants of some α-amino acids in ethanol–water mixtures. Anal. Biochem. 309, 75–78 (2002)
Barbosa, J., Barron, D., Beltran, J.L., Buti, S.: On the role of solvent in acid–base equilibria of diuretics in acetonitrile–water mixed solvents. Talanta 45, 817–827 (1998)
Barbosa, J., Toro, I., Sanz-Nebot, V.: Acid-base behavior of tripeptides in solvent used in liquid chromatography. Correlation between pK values and solvatochromic parameters of acetonitrile–water mixtures. Anal. Chim. Acta 347, 295–304 (1997)
Demirelli, H.: On the role of the solvent and substituent on the protonation equilibria of di-substituted anilines in dioxane–water mixed solvents. J. Solution Chem. 34, 1283–1295 (2005)
Buhvestov, U., Rived, F., Rafols, C., Bosch, E., Roses, M.: Solute–solvent and solvent–solvent interactions in binary solvent mixtures. Part 7. Comparison of the enhancement of the water structure in alcohol–water mixtures measured by solvatochromic indicators. J. Phys. Org. Chem. 11, 185–192 (1998)
Taft, R.W., Abboud, J.L.M., Kamlet, M.J.: Linear solvation energy relationships. 28. An analysis of Swain’s solvent “acidity” and “basicity” scales. J. Org. Chem. 49, 2001–2005 (1984)
Kamlet, M.J., Abboud, J.L.M., Abraham, M.H., Taft, R.W.: Linear solvation energy relationships. 23. A comprehensive collection of the solvatochromic parameters, π ∗, α, and β, and some methods for simplifying the generalized solvatochromic equation. J. Org. Chem. 48, 2877–2887 (1983)
Puranik, S.M., Kumbharkhane, A.C., Mehrota, S.C.: The static permittivity of binary mixtures using an improved Bruggeman model. J. Mol. Liq. 59, 173–177 (1994)
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Shamel, A., Saghiri, A., Jaberi, F. et al. Solvent Effects on Tautomeric and Microscopic Protonation Constants of Glycine in Different Aqueous Solutions of Methanol and Ethanol. J Solution Chem 41, 1020–1032 (2012). https://doi.org/10.1007/s10953-012-9845-0
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10953-012-9845-0