GAMMA-RESORCYCLIC ACID, ITS MONOHYDRATE AND ITS PYRIDINIUM COMPLEX

The crystal structures of gamma-resorcyclic acid (2,6-dihydroxybenzoic acid), C7H6O4, (I), gamma-resorcylic acid monohydrate, C7H6O4.H2O, (I I), and pyridinium gamma-resorcyulate, C5H6N+.C7H5O4-, (III), have bee n determined. In (I) and (II), the carboxyl group of the gamma-resorcy lic acid molecule is in an anti conformation and the carboxylic OH gro up is involved as a donor in an O-H...O intramolecular hydrogen bond. This bond is part of an infinite hydrogen-bonded chain with mixed sigm a- and pi-bond cooperativity. Structure (II) is disordered and may be considered to result from the superposition of two lower-symmetry stru ctures related by a mirror plane. Structure (III) consists of discrete complex units formed from the anion and cation by means of an N-H...O hydrogen bond.