Quantitative model of solvent effects on hydroxypyridine-pyridone and mercaptopyridine-thiopyridone equilibriums: correlation with reaction-field and hydrogen-bonding effects

Beak, Peter; Covington, Johnny B.; White, Jonathan M.

doi:10.1021/jo01296a001

Cited by 65 publications

(34 citation statements)

References 3 publications

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“…A great number of computational studies (see refs. ) have dealt with this tautomeric equilibrium by using both DFT and ab initio methods, and as Stanovnik et al. summarized previously, the results are greatly dependent on the method and the basis set used.…”

Section: Resultsmentioning

confidence: 99%

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

Calabrese

Maris

Uriarte

et al. 2016

Chemistry A European J

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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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Section: Resultsmentioning

confidence: 99%

“…The simplest model system with significant biological role is 2‐hydroxypyridine/2‐pyridone (2HP), and it has been the object of numerous studies . Three tautomeric structures are plausible: two lactim forms (OH) and a lactam species (C=O).…”

Section: Introductionmentioning

confidence: 99%

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

Calabrese

Maris

Uriarte

et al. 2016

Chemistry A European J

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“…The lactim tautomer is a better hydrogen bond donor and acceptor and predominates as a solvated monomer in polar or protic media. 18 In apolar solvents, the tautomeric equilibrium is influenced by dimerisation. Due to its polar nature, the lactam tautomer exists predominantly as a hydrogen-bonded dimer in apolar media.…”

Section: Resultsmentioning

confidence: 99%

N- vs. O-alkylation on 4,6-Dimethyl-2-oxo/Thio-nicotinonitrile

Dubey¹,

Tewari²

2010

Journal of the Korean Chemical Society

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“…Izučavanjem ravnoteže 2-piridon/2-hidroksipiridin u rastvaračima različite polarnosti utvrđeno je da povećanje polarnosti rastvarača pomera tautomernu ravnotežu ka piridonskom obliku [24][25][26]. Ovaj oblik je polarniji od hidroksi oblika, što je posledica razdvajanja naelektrisanja u rezonancionom hibridu 2-piridona.…”

Section: -Piridon/2-hidroksipiridin Tautomerija Kod Arilazo Piridonsunclassified

Azo-hydrazone tautomerism of aryl azo pyridone dyes

Mirković¹,

Ušćumlić²,

Marinković³

et al. 2013

Hem Ind

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In the last three or four decades disperse dyes derived from pyridones (in particular azo pyridone dyes) have gained in importance, and are widely used in various fields. These compounds have excellent coloration properties, and are suitable for the dyeing of polyester fabrics. Basic features of these dyes are simplicity of their synthesis by diazotation and azo coupling. They generally have high molar extinction coefficient with medium to high light and wet fastness. The absorption maxima of these dyes show their visible absorption wavelength ranging from yellow to orange, which can be attributed to poorly delocalized electrons in the pyridone ring. However, there are several dyes with deep colors such as red or violet. Pyridone dyes with alkyl and aryl groups in ortho position to azo group show 2-pyridone/2-hydroxypyridine tautomerism, while those containing OH and NHR groups conjugated with the azo group show azo-hydrazone tautomerism. Determining azo-hydrazone tautomerism could be therefore interesting, since the tautomers have different physico-chemical properties and most importantly different coloration. The literature on azo-hydrazone tautomerism, determination of equilibrium position, and investigation of substituent and solvent influence on tautomerism has been summarized in the presented review. The general conclusion is that the equilibrium between two tautomers is influenced by the structure of the compounds and by the solvents used. The tautomeric behavior patterns of the arylazo pyridone dyes in the reviewed literature has been studied using various instrumental techniques, including FT-IR, UV-vis, and NMR spectroscopy. The quantum chemical calculations related to the azo-hydrazon tautomerism have also been included. A large number of pyridone dyes exist in hydrazone form in solid state, while in solvents there is a mixture of tautomers. In addition, the X-ray single-crystal diffraction data analysis of some commercial pyridone dyes has been discussed concluding that they all crystallize in the hydrazone form

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Quantitative model of solvent effects on hydroxypyridine-pyridone and mercaptopyridine-thiopyridone equilibriums: correlation with reaction-field and hydrogen-bonding effects

Cited by 65 publications

References 3 publications

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

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

N- vs. O-alkylation on 4,6-Dimethyl-2-oxo/Thio-nicotinonitrile

Azo-hydrazone tautomerism of aryl azo pyridone dyes

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