Solid state annular tautomerism in a molecule containing two imidazole moieties

Drew, M. G. B., Das, D., De, S., Naskar, J. P. and Datta, D. (2008) Solid state annular tautomerism in a molecule containing two imidazole moieties. Journal of Chemical Crystallography, 38 (7). pp. 507-512. ISSN 1074-1542 doi: 10.1007/s10870-008-9322-1

Abstract/Summary

The X-ray crystal structure of the 1:2 condensate (1) of hydrazine hydrate and 4-methyl-imidazole-5-carboxaldehyde has been determined. The molecule is centrosymmetric crystallising in the space group Fddd with cell dimensions: a = 10.557(14), b = 17.062(22), c = 24.759(27) angstrom. Fourier map shows that the NH hydrogen atom of each imidazole moiety has equal possibility of occupying any of its two ring N atoms. This poses the possibility of finding three tautomers in 1 in the solid state. Consideration of the H-bonding pattern observed in 1 and related B3LYP/6-311+G(2d, p) calculations show that only two tautomers are present in the solid state. The situation is compared with that in the structure of 4(5)-nitro-5(4)-methoxy-imidazole reported previously by Kubicki.