Carbon-13 nuclear magnetic resonance of the azomethine group. II—(II.II) conjugation and twist angles

Torsional angles in some mono-substituted conjugated benzenes were determined from the chemical shift of the para carbons. Similar results were obtained from ketones and imines, and the torsional angles increase, as expected, with steric hindrance. It is possible to assign a syn or anti stereochemistry for the imines from the value of the torsional angle.