Hydrogen bonding and tautomerism of benzylideneanilines in the solid state

Abstract

The 13C cross-polarization magic angle spinning NMR spectra of N-(2′-hydroxybenzylidene)-2-hydroxyaniline (1), N-(2′-hydroxybenzylidene)-4-nitroaniline (2) and N-(4′-dimethylaminobenzylidene)-2-hydroxy-­aniline (3) indicate a keto–hydroxy tautomerism of 1 but not of 2. This was confirmed by a single-crystal x-ray diffraction study of 1, which revealed that the two distinct molecules in the unit cell are linked by intermolecular hydrogen bonding. The presence of this bonding may explain the occurrence of the keto–hydroxy tautomerism. Copyright © 1999 John Wiley & Sons, Ltd.