Title: Tautomérie De Pyrazoline‐5‐Thiones N<sub>1</sub>‐Substituées
Abstract: Abstract The tautomerism of alkyl and/or arylpyrazolin‐5‐thiones, which can exist under three prototropic forms (CH, NH, SH) is examined by N. M. R., I. R. and U. V. spectroscopy. The equilibrium takes place between the SH and NH tautomers: in neutral solvents, the SH isomer is predominant while in aprotic basic media, the ratio [NH]/[SH] depends upon, several polarity parameters. In protic media (alcohols),the percentage of the NH form increases with the hydrogen bond donating power of the solvent. Some substituents (acyl‐, phenylazo‐) are able to stabilize one of the tautomers via an intramolecular bond. The differences in the tautomeric behaviour between pyrazolin‐5‐ones and 5‐thiones are discussed in terms of relative polarity and stability of the carbonyl and thiocarbonyl groups.
Publication Year: 1977
Publication Date: 1977-01-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 8
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