Molecular conformation and electronic structure of azomethines. Part 5. Determination of the conformation of some N-methylimine derivatives of aldehydes and ketones from dipole moment data

Abstract

The dipole moments of some N-methylimine derivatives of aldehydes and ketones have been measured in benzene and analysed in terms of the configuration of the CN bond and the conformation on the Ph–C bond. The evidence presented here suggests that a σ–π approximation is sufficient for dipole moment calculations as far as conformational assignments are concerned. The dipole moment analysis yields unambiguous conformational assignments in the presence of a single configuration. When a configurational equilibrium is present, an additional molecular property, e.g. n.m.r., must be employed; this additional datum on the isomer ratio allows the most probable conformation to be selected by the dipole moment analysis.