Abstract
Properties of some polyhydrazido-acids in DMF and DMF-water solutions and their transformations under the influence of an acetic anhydride-pyridine mixture have been investigated. The polyhydrazido-acids have been obtained from the dihydrazide of (-) (1R,2R) trans-1,2 cyclopropanedicarboxylic acid and the dianhydride of pyromellitic (PHA-I) or 3,3′, 4,4′-diphenyloxide tetracarboxylic (PHA-II) acids and from a model hydrazido acid (MHA) prepared from the same hydrazide and phthalic anhydride. Cooperative changes in the molar rotation [π] and [η] were found in a mixed DMF-water solvent when the solvent composition was varied. These changes are related to intramolecular cooperative conformational transitions of the coil-compact particle type. PHA-II and MHA are used as examples showing that, under the influence of an acetic anhydride-pyridine mixture, cyclodehydration occurs via the formation of amidoisoimide which is isomerized further to amidoimide. When the acetic anhydride-pyridine mixture is present in large excess, the process ends with the acetylation of an amide group adjacent to the three-membered ring.
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