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NMR characterization of hydrate and aldehyde forms of imidazole-2-carboxaldehyde and derivatives
Juan Manuel Lázaro Martínez1, Pablo Nicolás Romasanta, Ana Karina Chattah
1Departamento de Química Orgánica, Facultad de Farmacia y Bioquimica, Universidad de Buenos Aires, Junin 956 (C1113AAD), Ciudad Autónoma de Buenos Aires, Argentina.
Abstract:
The existence and stability of the aldehyde-hydrate form of imidazole-2-carboxaldehyde (4) were studied using FTIR together with solution- and solid-state NMR experiments. The results allowed us to conclude that the hydrate form was stable and precipitated at pH = 8.0 and that the aldehyde form was isolated at pH = 6.5 and 9.5. Moreover, the presence of the aldehyde-hydrate form was studied through NMR experiments in D(2)O at both alkaline and acidic pH. In addition, the tautomeric forms of the 2-substituted imidazole compounds were also analyzed to investigate the influence of the hybridization on the carbon adjacent to the imidazole ring, by (13)C NMR in DMSO-d(6), acetone-d(6), and CDCl(3). The presence of the syn- and anti-isomers of oxime 8 obtained from 4 were characterized by solid-state NMR and variable-temperature NMR experiments in acetone-d(6).
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