3-[(Z)-(4-Diethylamino-6-oxocyclohexa-2,4-dien-1-ylidene)methylamino] benzoic acid

Abstract

The title compound, C18H20N2O3, crystallizes as the keto tautomer, unlike the vast majority of similar structures that have been reported that contain the hydr-oxy tautomer. There are two strong hydrogen bonds in the crystal structure, both accepted by the same carbonyl group: one intra-molecular N - H⋯O and one inter-molecular O - H⋯O. As a result, the carbonyl C=O distance is long, at 1.310 (2) Å, which may suggest the mol-ecule has a significant zwitterionic character. The dihedral angle between the benzene ring planes is 15.05 (7)°. As a result of the intramolecular hydrogen bond, the bridging C - C=N - C group is almost coplanar with the benzene ring that has the diethylamino substituent [dihedral angle 2.35 (15)°]. © International Union of Crystallography 2008.