Conformational comparison of aromatic molecules and their ions. III N-(Diphenylmethylene)-aniline and benzil by NMR and EPR

Abstract

Utilizing methods of conformational analysis developed from Johnson-Bovey tables and the Fraenkel electron density-chemical shift relation, the dihedral angle of the A ring of N-(diphenylmethylene)-aniline I is found to have its average position near that of benzalaniline, i.e., nearly vertical. Due to a complex spectrum, the geometries of the other rings are difficult to assess. The dianion I−2 shows a large chemical shift from I owing to the high negative charge. The average positions of the phenyl rings of benzil (II) are confirmed by NMR to be perpendicular to each other and those of II−2 to be nearly parallel to each other, but perpendicular to the plane of the cis chelate.