Pyrid-2-thione

The determination of the structure of adenine hydrochloride (see Volume 2, Section IV,K, of article IV by Katritzky and Lagowski) is an example of extremely accurate X-ray crystallography whereby the positions of individual hydrogen atoms were located. An example of the deduction of structure from bond lengths between heavy atoms is provided by Penfold s investigation of pyrid-2-thione. ... 

In 1951, pyrid-4-thione was concluded from ultraviolet spectral data to exist predominantly as such in ethanolic solution,but no comparisons were made and this conclusion had to be considered as tentative. Pyrid-2-thione has been shown by X-ray crystallography to exist as hydrogen-bonded dimers (201) in the solid state, the posi-... 

Pyridyl sulfides can be prepared by reaction of alcohols with l-methyl-2-fluoropyridinium tosylate and base followed by reaction with pyrid-2-thione (equation TV). ... 

The electronic spectrum of a compound arises from its 7r-electron system which, to a first approximation, is unaffected by substitution of an alkyl group for a hydrogen atom. Thus, comparison of the ultraviolet spectrum of a potentially tautomeric compound with the spectra of both alkylated forms often indicates which tautomer predominates. For example, Fig. 1 shows that 4-mercaptopyridine exists predominantly as pyrid-4-thione. In favorable cases, i.e., when the spectra of the two alkylated forms are very different and/or there are appreciable amounts of both forms present at equilibrium, the tautomeric constant can be evaluated. By using this method, it was shown, for example, that 6-hydroxyquinoline exists essentially as such in ethanol but that it is in equilibrium with about 1% of the zwitterion form in aqueous solution (Fig. 2). 

English and Australian investigators showed simultaneously that the pyrid-2- and -4-thione forms predominate in aqueous solution by factors of ca. 10 (see Table V) by comparative studies of these... 

A careful analysis of n.m.r. spectra measured in various solvents has revealed the occurrence of ring-chain tautomerism in 1,3,4-thiadiazolidine-2-thiones (141). In solution, these compounds exist in equilibrium with their open-chain hydrazone -tautomers (142) the equilibrium is displaced entirely to the hydrazone salt form (143) in alkaline media. The discovery was made with 5-(pyrid-2-yl)-l,3,4-thiadiazolidine-2-thione (141 = R = H R = 2-C6H4N), the alkali and amine salts of which... 

Pyridonimine, 1-hydroxy-, see Amino-pyridine 1-oxide Pyridoxal, 354, 355 Pyridoxine, 354, 355 Pyrid-2- and -4-thiones, 328, 333, 396-398... 

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