Special aspects of the course of thermal cyclodehydration of polyhydrazide acids in the solid phase in presence of residual solvent and in solutions

IR spectroscopy and spectropolarimetry have been used to study the conversion of the polyhydrazide acids based on racemic and optically active (1R, 2R)-trans-1,2-cyclopropanedicarboxylic acids and the dianhydrides of pyromellitic and 3,3′4,4′-diphenyloxidetetracarboxylic acids in the course of thermal cyclodehydration in solutions and in the solid phase in presence of residual solvent. It is shown that in the solid phase and in solution in pyridine the thermal cyclodehydration of the polyhydrazide acids directly leads to a polyamidoimide and in solutions in amide solvents and DMSO the process passes through the intermediate formation of isoimide groupings with their subsequent isomerization to imide rings.