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Thermodynamic characterization of tautomeric equilibria by multinuclear magnetic resonance. Application to 3-hydroxypyridine

✍ Scribed by Juan Llor; Obdulio Lopez-Mayorga; Luis Muñoz

Publisher: John Wiley and Sons
Year: 1993
Tongue: English
Weight: 466 KB
Volume: 31
Category: Article
ISSN: 0749-1581
DOI: 10.1002/mrc.1260310607

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✦ Synopsis

Abstract

A marked temperature dependence of the ^13^C and ^15^N chemical shifts of 3‐hydroxypyridine in D~2~O (pD = 7.0) was observed. This dependence is explained in terms of thermally induced equilibrium shifts between the neutral form and the zwitterionic form of 3‐hydroxypyridine. A method was developed to characterize the thermodynamics of the equilibria that are rapid on the NMR time scale, using the observed average ^13^C and ^15^N chemical shifts at different temperatures. This method was applied to the thermodynamics of the tautomerization equilibria of 3‐hydroxypyridine. The equilibrium constants and the standard enthalpy change of the tautomerization equilibrium obtained by ^13^C and ^15^N methods agree very well with the results obtained by other spectroscopic methods.

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