Tautomerism of aza cycles: I. Structure of 3(5)-butylsulfanyl-5(3)-methyl(phenyl)-1H-1,2,4-triazole tautomers in crystal. Preference of the 3-RA-5-RD-1H-tautomer of 3(5)-mono-and 3,5-disubstituted 1,2,4-triazoles |
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Authors: | B I Buzykin E V Mironova V N Nabiullin A T Gubaidullin I A Litvinov |
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Institution: | (1) Arbuzov Institute of Organic and Physical Chemistry, Kazan Research Center, Russian Academy of Sciences, ul. Arbuzova 8, Kazan, 420088, Tatarstan, Russia |
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Abstract: | The X-ray diffraction study of potentially tautomeric 3(5)-butylsulfanyl-5(3)-methyl-1H-1,2,4-triazole and its 5(3)-phenyl-substituted analog showed that these compounds in crystal have the structure of 3-butylsulfanyl-5-methyl(phenyl)-1H-tautomers. Analysis of our experimental and published data indicated that 3(5)-monosubstituted 1,2,4-triazoles and 3,5-disubstituted derivatives having nonequivalent substituents in crystal as exist as a tautomer in which the electron-acceptor substituent (RA) occupies the 3 position, while the electron-donor substituent (RD) resides in the 5 position, i.e., as 3-RA-5-RD-1H-1,2,4-triazoles. Symmetric 3,5-disubstituted 1,2,4-triazoles could give rise to tautomeric equilibrium between the 1H-and 2H-structures even in crystal. |
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