Dipolar Characteristics of the Imine‐Group and its Hydrogen Bonds. A Quantum‐Chemical and Experimental Approach

The dipole moments of two aliphatic imines and their hydrogen bonded phenol complexes were determined experimentally. A value of 1.63 D was found for isopropyl, N isopropyl imine and 1.60 D for tertio butyl, N isobutyl imine. Their complexes with phenol, 3,5 dichloro- and para nitro phenol are respectively of 3.45, 4.57 and 6.99 D for the first and 3.69, 4.67 and 7.10 D for the second. This experimental study was completed by a theoretical study of model imines and their complexes with watermethanol and formic acid. The theoretical results explain through structural and electronic arguments the variation of the dipole moments. They furnish also values of the angles which are indispensable for the discussion of experimental dipole increments. The dipole increments obtained show clearly the strength of the H-bond obtained with imine bases as well as its sensibility to the strength of the associated acid.