NMR Characterization of Hydrate and Aldehyde Forms of Imidazole-2-carboxaldehyde and Derivatives

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).

A time-resolved study of the multiphase chemistry of excited carbonyls: Imidazole-2-carboxaldehyde and halides

“…The known impurity of bi-imidazole in the commercial imidazole-2-carboxaldehyde did not notably interfere, since no absorption for triplet state bi-imidazole was detected. In our conditions, aqueous solutions of pH 6.5, IC is expected to be in its aldehyde form [30].…”

Paramagnetic solid-state NMR assignment and novel chemical conversion of the aldehyde group to dihydrogen ortho ester and hemiacetal moieties in copper(ii)- and cobalt(ii)-pyridinecarboxaldehyde complexes

“…In particular, nitrogen heterocycles such as imidazole and pyridine molecules containing carbonyl or its hydrated groups known as gem-diols are widely used, due to their coordination properties, [1][2][3][4] especially in catalysis and environmental chemistry. Working with this kind of system is a challenge since the instability of gemdiol [5][6][7][8][9][10] creates uncertainty over the form of the ligand, hence careful characterization is particularly important. 9,[11][12][13][14] Taking into account the key role of NMR spectroscopy in characterizing the chemical structure of new compounds, copper and cobalt complexes containing this type of ligand are a challenge for this technique.…”

Vapor‐Phase Linker Exchange of the Metal–Organic Framework ZIF‐8: A Solvent‐Free Approach to Post‐synthetic Modification

“…2-Methyl imidazole (HmIm) and CHO-HIm have similar dimensions, small enough to allow diffusion through the ZIF pore network (Table S1). As CHO-Im is prone to side-reactions, [13][14][15] VPLE trials (24 h) were performed at different temperatures. Reaction at 353 and 373 K resulted in a yellow ZIF powder, similar to what is obtained through direct synthesis or PSLE with CHO-HIm in solution.…”