The features of imide heterocycle formation from a substrate and other basic product – dinitrile were analysed and summarized at ammoxidation of o-xylene and 4-brom- and 4-phenyl-o-xylene as well. It was found that in both cases imide heterocycle formation occurs due to a spatial effect connected with location of side ortho-groups at a shorter distance from each other, permitting their intramolecular interaction. It has been revealed that the effect of spatial facilitation of ortho-methyl substitutes of the substate and ortho-nitrile functional groups of dinitrile is connected with oxidative cyclization, respectively, in the conditions of ammoxidation and under the influence of water as the product of attendant reactions of the process of oxidative dehydrogenation and deep oxidation.