Dipole moment and electron distribution of the amide group

Abstract

Dipole moments of five substituted N,N-dimethylbenzamides Ia-Ie were measured in benzene and dioxan solutions. The group moment of 12.7 . 10 -30 C m (at an angle of 80° to the C (1) -C bond) was resolved into components and a mesomeric moment of 4.7 . 10 -30 C m (in the direction from N to C) was derived, accounting for the conjugation within the dimethylamide group. A smaller mesomeric moment in the same direction was found for the unsubstituted amide group. The results are but roughly consistent with an interpretation in terms of the mesomeric formulae A ##e B .