Abstract
The resolution of electronic spectra using log-normal curves has permitted a quantitative description of the equilibria of pyridoxal, one of the vitamin B6 molecules, and of the related 5-deoxypyridoxal in solution. Tautomeric, hydration and hemiacetalization equilibrium constants for water-dioxane mixtures of these compounds are reported (0–70% weight fraction in dioxane) at temperatures ranging from 10°C to 50°C. These results provide the standard thermodynamic function changes for the indicated processes in the different mixtures studied. The aldehyde content in the two compounds increases concomitantly with the dioxane content of the solution and also when it changes from the cationic to the anionic species. 5-deoxypyridoxal becomes significantly more hydrated in its more protonated form, K h (+a)/K h (±a)≈7–8, as do other aldehydes. Hemiacetalization in pyridoxal follow a similar pattern, K he (±a)/K he (−a)≈20–30, due principally to differences in the enthalpy contribution. Hemiacetalization is favored over hydration by ∼20.6 kJ-mol−1 in water solution.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
P. Christen and D. E. Metzler,Transaminases, (Wiley, New York, 1985), p. 65.
E. E. Snell, inVitamin B-6 Pyridoxal Phosphate: Chemical, Biochemical and Medical Aspects, D. Dolphin, R. Poulson and O. Avramovic, eds., Part. A (Wiley, New York, 1986).
C. M. Metzler, A. Cahill, and D. E. Metzler,J. Am. Chem. Soc. 102, 6075 (1980).
D. E. Metzler, C. M. Harris, R. J. Johnson, C. B. Siano, and J. A. Thomson,Biochemistry 12, 5377 (1973).
C. M. Harris, R. J. Johnson, and D. E. Metzler,Biochim. Biophys. Acta 421, 181 (1976).
M. Cortijo, J. Llor, and J. M. Sanchez-Ruiz,J. Biol. Chem. 263, 17960 (1988).
J. M. Sanchez-Ruiz, J. Llor, and M. Cortijo,J. Chem. Soc. Perkin Trans. II 2047 (1984).
J. M. Sanchez-Ruiz, S. Asensio, J. Llor, and M. Cortijo,J. Chem. Soc. Perkin Trans. II 169 (1987).
J. Llor, J. M. Sanchez-Ruiz, and M. Cortijo,J. Chem. Soc. in Perkin Trans. II 951 (1988).
A. R. Katritzky and M. Karelson,J. Am. Chem. Soc. 113, 1561 (1991).
P. Cieplak, P. Bash, U. C. Singh, and P. A. Kollman,J. Am. Chem. Soc. 109, 6283 (1987).
K. Nagano and D. E. Metzler,J. Am. Chem. Soc. 89, 2891 (1967).
R. J. Johnson and D. E. Metzler,Methods Enzymol. 18A, 433 (1970).
D. E. Metzler, C. M. Harris, R. L. Reeves, W. H. Lawton, and M. S. Maggio,Anal. Chem. 49, 864A (1977).
C. Iwata,Biochem. Prep. 12, 117 (1968).
N. Nakamoto and A. E. Martell,J. Am. Chem. Soc. 81, 5863 (1959).
E. A. Peterson and H. A. Sober,J. Am. Chem. Soc. 76, 169 (1954).
W. Korytnyk and R. P. Singh,J. Am. Chem. Soc. 85, 2813 (1963).
I. D. Lapper, H. H. Mantsch, and I. C. P. Smith,Can. J. Chem. 53, 2406 (1975).
K. Nagano and D. E. Metzler,J. Am. Chem. Soc. 89, 2891 (1967).
J. Llor, J. M. Sánchez-Ruiz, M. Cortijo, and B. Clares,An. Quim. 80, 701 (1984).
J. M. Sanchez-Ruiz, J. Llor, E. Lopez-Cantarero, and M. Cortijo,An. Quim. 80, 708 (1984).
W. L. Marshall and A. S. Quist,Proc. Natl. Acad. Sci. 58, 901 (1967).
A. S. Quist and W. L. Marshall,J. Phys. Chem. 72, 1536 (1968).
W. L. Marshall,J. Phys. Chem. 74, 346 (1970).
E. C. W. Clarke, and D. N. Glew,Trans. Faraday Soc. 62, 539 (1966).
R. A. McClelland, P. Sukhai, K. M. Engell, and P. E. Sorensen,Can. J. Chem. 72, 2333 (1994).
S. Cabani, P. Gianni, and E. Matteoli,J. Phys. Chem. 76, 2959 (1972).
V. Okano, H. E. Toma, and L. do Amaral,J. Org. Chem. 46, 1018 (1981).
K. B. Wiberg, K. M. Morgan, and H. Maltz,J. Am. Chem. Soc. 116, 11067 (1994).
Y. Pocker, J. E. Meany, and B. J. Nist,J. Phys. Chem. 71, 4509 (1967).
J. Llor and S. B. Asensio,J. Solution Chem. 24, 1293 (1995).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Llor, J., Asensio, S.B. Thermodynamics of the tautomeric, hydration and hemiacetalization of 5-deoxypyridoxal and pyridoxal in water-dioxane mixtures. J Solution Chem 25, 667–679 (1996). https://doi.org/10.1007/BF00972681
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00972681