engleski

Structural investigation of aroylhydrazones by NMR spectroscopy

Aroylhydrazones have been intensively investigated for years due to their versatile properties and applications. Recent studies have shown that nicotinic acid hydrazones could be considered as anti-inflammatory and analgesic agents, 1 and as a novel pharmacophore in the design of anticonvulsant drugs.2 In this work one and two dimensional 1H, 13C and 15N NMR spectroscopy was used for structural characterization of aroylhydrazones derived from nicotinic acid hydrazide and 2, 3- dihydroxybenzaldehyde (1), 2, 5- dihydroxybenzaldehyde (2), 2-hydroxy-4-methoxy- benzaldehyde (3), 3-chloro-2- hydroxybenzaldehyde (4) and 5-nitro-2- hydroxybenz-aldehyde (5). In most solvents all compounds are in most stable enolimino tautomeric form. However, in absorption spectra of 5 in DMSO the band around 400 nm appeared, indicating the presence of ketoamino tautomeric form. In addition, the prominent changes in the absorption spectra were observed during the time, but only if the solution was exposed to light. These spectral changes can be assigned to the E/Z photoisomerisation. For the identification of different forms, NMR spectroscopy was used.

aroylhydrazones; NMR; structure; isomerization

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