Effects of Chlorination on the Tautomeric Equilibrium of 2‐Hydroxypyridine: Experiment and Theory

Abstract

What is the most significant result of this study? This work explores the intramolecular proton transfer in the tauto-meric/conformational equilibria of ab iological model system. Previous experiments and theory gave contradictory and nonconclu-sive results due to the subtle balance of inductive and mesomeric effects. In this study,t he role of halogenation at different ring positions and the influence of the solvent on the position of complex conformational and tautomeric equilibria are explored. How did each team contribute to the work? This work stems from ac ollaboration between two research groups, triggered by the Marco Polo exchange program in which Camilla Calabrese participated as aP hD student. The presented results could not be reached without the contributions of each team. The experimental part was performed with the use of two different microwave spectrometers (one at the University of Bolo-gna (Italy) and the other one at the University of the Basque Country (Spain)). The full potential of the spectral range, resolution, and sensitivity had to be exploited for the characterization of the different tautomers and conformers of the chlorine-substituted hydroxy-pyridines in the gas phase, which presents an environment free of intermolecular interactions. The results of extensive quantum chemical calculations both in the gas and in the solvent phases have been the input for the rationalization of the effects of chlori-nation at different positions of the ring. Does the research open other avenues that you would like to investigate? The results were extremely interesting and exciting, and we intend to investigate other examples of molecules that present ac omplex conformational surface, in which substitution of atoms or groups of atoms can have adrastic influence on the stability of the various structural forms. Moreover,w ew ould like to explore the influence of such substitutions on the properties related to intermolecular interactions and reactivity. Invited for the cover of this issue are the groups of EmilioJ.C ocineroa nd Sonia Melandri at the University of PaísV asco and the University of Bologna. The image depicts different possibilities that this tautomeric equilibrium can take according to the differentp ositions of the chlorinea tom, which, in manycases,are difficult to predictapriori. Read the fulltext of the article at

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