The reaction of imidazole with hexachlorocyclotriphosphazene (I) has yielded hexakis(imidazolyl)cyclotriphosphazene (II). Compound II has been studied as a model for the analogous linear high polymer which is a prospective biodegradable carrier macromolecule. Compound II is hydrolytically unstable and decomposes to hydroxyphosphazenes, imidazole, and phosphate in aqueous media. A kinetic analysis of the removal of the first imidazolyl group from II in unbuffered 20% aqueous tetrahydrofuran within the pH range of 6.5-7.8 has shown that the hydrolysis is autocatalyzed by the free imidazole liberated in this step. Initially, the displacement of imidazole is a first-order process with respect to [II], but the release of imidazole gives rise to faster, second-order reaction in which the rate depends on the first powers of [II] and [imidazole]. The evidence favors the influence of free imidazole as a general-base catalyst and not via the formation of hydroxide ion. TV-Methylimidazole reacts with I to form an unusual series of highly reactive yellow salts of the general formula [N3P3Cl6-x(C4H6N2)x]x+xCl (VII). The chemistry of II and VII is discussed in terms of its relationship to the synthesis and reactions of the analogous linear high polymeric phosphazenes.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry