F. Mansilla-Koblavi, J. A. Tenon, S. Toure
Aug 15, 1995
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0
Influential Citations
15
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Journal
Acta Crystallographica Section C-crystal Structure Communications
Abstract
The crystal structures of five N-(2,3-dihydroxybenzylidene)amine derivatives, C 7 H 6 NO 2 -R [R = phenyl (1), p-methylphenyl (2), o-chlorophenyl (3), isopropyl (4) and cyclopropyl (5)] are presented and discussed. [IUPAC names : 3-(phenyliminomethyl)- (1), 3-(4-tolyliminomethyl)- (2), 3-(2-chlorophenyliminomethyl)- (3) and 3-(cyclopropyliminomethyl)-1,2-benzenediol (5), and 2-hydroxy-5-(isopropylaminomethylene)-2,4-cyclohexadien-1-one (4).] All the molecules are characterized by the presence of a strong intramolecular hydrogen bond, O-H...N, which determines the formation of a six-membered pseudocycle in the same plane as the phenolic moiety. When R is an aromatic ring, the molecules are either planar or make a dihedral angle which does not exceed 10°. Except for (2), all the molecules are associated as dimers with two intermolecular O-H...O hydrogen bonds involved in a ten-membered pseudocycle. In compound (5), an intermolecular hydrogen bond with a third molecule is also observed. In (2), the cohesion of the crystal is mainly secured by the intermolecular hydrogen bond between the hydroxyl group and the aromatic p-methylphenyl ring. Unlike the N-(2-hydroxybenzylidene)amines for which the phenolic tautomer largely prevails, in the present compounds the quinonic form is present in significant amounts and is even dominant for compound (4). Hence the presence of a second vicinal hydroxyl group determines an important shift in the tautomeric equilibrium.