Collect. Czech. Chem. Commun. 1979, 44, 2494-2506

Hydrogen bonding, configuration and conformation of substituted α-oxo oximes and hydrazones

Otto Exnera, Jorga Smolíkováa, Václav Jehličkab and Ahmad S. Shawalic

a Institute of Organic Chemistry and Biochemistry, Czechoslovak Academy of Sciences, 166 10 Prague 6, Czechoslovakia
b Department of Physical Chemistry, Prague Institute of Chemical Technology, 166 28 Prague 6, Czechoslovakia
c Department of Chemistry, Faculty of Science, University of Cairo, Giza, Egypt


Substituted 2-bromo-1-phenylglyoxal 2-phenylhydrazones IIIa-f exist in tetrachloromethane or benzene solutions prevailingly in E-configuration and in conformation A with an intramolecular hydrogen bond. The latter was evidenced by the N-H valence frequency at 3 290 cm-1 and by 1H NMR shifts with reference to derivatives without a carbonyl group - α-chlorobenzaldehyde phenylhydrazones V. From dipole moments of IIIa-d, measured in benzene solution, the contribution of the hydrogen bondH) was evaluated to 17 . 10-30 C m. This quantity is twice larger than in any other reported compound but the direction of the vector is as usual: approximately from H to N. In structurally similar derivatives of hydroxylamine, substituted 2-phenylglyoxylhydroximoyl chlorides IVa-d, no intramolecular hydrogen bond was detected; the dipole moments found were interpreted in terms of the Z-configuration and the prevailing conformation G.