STRUCTURE, NATURE OF HYDROGEN BONDING, AND ZE STEREODYNAMICS OF o-INDOPHENOLS

Article abstract of DOI:10.1007/BF00753037

X-ray diffraction analysis was used to determine the structure of o-indophenol, C20H24N2O4 (R=0.054 relative to 4281 reflections).The crystal consists of dimers, which form hydrogen bonds with intra- and intermolecular components.IR and PMR spectroscopy shows that the formation of intra- and intermolecular O-H ...N hydrogen bonds by o-indophenol molecules depends on their aggregate state (crystalline state in solution) and steric and electronic effects of the substituent in the phenolic fragment.The p-quinonimine and phenol rings are acoplanar in dimers with intermolecular hydrogen bonds.All the o-indophenols in solution form intramolecular hydrogen bonds with coplanar or almost coplanar conformation of the quinonimine and phenol fragments.The strength of the intramolecular hydrogen bonds determines the predominance of a torsion (T) or inversion (I) mechanism for the degenerate Z <*> E isomerization of o-indophenols or the replacement of the I and T channels for stereoconversion upon change in the solution temperature.