There have been generalized and analysed the particularities of formation of the imido-o-phthal acid at the heterogeneous oxidation and oxidative  ammonolysis of different classes of compounds. It has been shown that  phthal-о-imide dependent on the used organic raw material can be obtained both as main and by product of reaction. It has been  established that the formation of imide cycle at the oxidation is connected with the presence of nitgorencontaining group or heteroatom–nitrogen in the initial substance, and at the oxidative ammonolysis – by the combination of various types of reactions of oxidation and ammonolysis in one process. In all cases formation of nitrogencontaining heterocycle of imide takes place as a result of intramolecular cycling of the surface oxygen-containing intermediate, which is formed from the initial o-xylene or compound close by structure