Synthesis, spectral and structural studies, and an evaluation of the hydrogen bonding of some phenylhydrazones

Abstract

A series of 46 phenylhydrazones, some novel, containing a variety of structural types has been synthesised. These have been studied by 1H n.m.r. and i.r. spectroscopy with respect to potential inter- and intra-molecular hydrogen bonding. ortho-Nitro or -carbonyl groups form strong hydrogen bonds to the imino-group which are readily observed by 1H n.m.r. but not by i.r. spectroscopy. ‘Terminal’ carbonyl groups also form strong hydrogen bonds to the imino-group and these can be detected by both i.r. and 1H n.m.r. spectroscopy. When both ortho-nitro- or -carbonyl groups and ‘terminal’ carbonyl groups are present the imino hydrogen atom is doubly hydrogen bonded and this is apparent in the 1H n.m.r. spectrum. The formation of an intramolecular hydrogen bond in the phenylhydrazone prevents the formation of an intermolecular hydrogen bond between the phenylhydrazone and a polar solvent.