Tautomeric equilibria, elucidation using

Tautomeric equilibria, elucidation using basicity measurements, 327 Tautomeric mixture composition of, 318 equilibrium position of, 318 influence of external factors on composition of, 318... 

One interesting problem frequently recurring in heterocyclic chemistry, particularly with respect to nitrogen heterocycles, is tautomeric equilibria. Too many methods are available for the elucidation of equilibrium positions and tautomeric equilibrium constants (Kj) to adequately review the whole question here. However, the Hammett equation provides one independent method this method has the advantage that it can be used to predict the equilibrium position and to estimate the equilibrium constant, even in cases where the equilibrium position is so far to one side or the other that experimental determination of the concentration of the minor component is impossible. The entire method will be illustrated using nicotinic acid as an example but is, of course, completely general. 

Intensive investigations have been conducted to elucidate the nature of the mechanism of thermochromism of salicylidene Schiff bases. Different techniques or methods suitable for the study of the tautomeric equilibrium between the end form and the (Z)-keto form have been used, including X-ray diffraction, NMR, infrared (IR) and Raman spectroscopy, and theoretical calculations. In the anil-... 

In this book, we have tried to put together a number of approaches to these topics, which, on one hand, highlight these problems, and, on the other, try to offer solutions to at least a few of them. In a number of chapters, tools are presented for the experimental and theoretical study of tautomerism absorption in combination with chemometrics to unravel the composition of a tautomeric mixture (Chapter 2) steady-state and time-resolved optical techniques to investigate transfer dynamics (Chapters 3 and 4) the use of NMR to elucidate equilibrium properties... 

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