Hydrogen bonding and tautomerism of benzylideneanilines in the solid state

The C-13 cross-polarization magic angle spinning NMR spectra of N-(2'-hydro xybenzylidene)-2-hydroxyaniline (1), N-(2'-hydroxybenzylidene)-4-nitroanili ne (2) and N-(4'-dimethylaminobenzylidene)-2-hydroxyaniline (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. T he presence of this bonding may explain the occurrence of the keto-hydroxy tautomerism. Copyright (C) 1999 John Wiley & Sons, Ltd.