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 D2O at both alkaline and ...