The aromaticity of heterocycles containing the imine nitrogen

The method of predicting aromaticity based on simple Hückel calculations is applied to heterocyclic systems which contain the imine nitrogen. The necessary heteroatom integrals were determined from thermochemical data. Replacement of C by N in alternant systems produced no dramatic changes, but in nonalternants the effect can be large and unexpected as in the azapentalenes where interesting synthetic possibilities are suggested.