The hydrolysis behavior of the aminocyclotriphosphazenes (NPR2)3, where R = NH2, NHCH3, NHCH2COOC2H5, NHCH2CONHCH3, N2C3H3 (imidazolyl), NHCH2CF3, NHCH2C6H5, NHC6H5, NC4H4 (pyrrolyl), NC4H8 (pyrrolidino), NC5H10 (piperidino), and NC4H8O (morpholino), has been examined in water or aqueous dioxane, acid, and base. The ease of hydrolysis in aqueous dioxane declined with changes in R in the order N2C3H3 > NHCH2COOC2H5 > NHC-H2CONHCH3 > NH2 > NHCH3 > NHC6H5 > NHCH2C6H5 > NHCH2CF3 > NC4H4, NC4H8, NC5H10, and NC4H8O. Two different but interconnected mechanistic pathways appear to be followed. In the first, hydrolytic removal of one amino residue from phosphorus occurs to yield species of type N3P3R5OH before cleavage of the phosphazene ring takes place. In the second, cleavage of the phosphazene ring is a fast reaction following protonation of the ring nitrogen atoms. Those compounds which contained amino acid ester or amide side groups hydrolyzed only after prior initial conversion of the ester or amide units to free carboxylic acid groups. Comparisons are made with the behavior of the open-chain high polymers of formula (NPR2)n, where R = NHCH3, NHCH3 and N2C3H3, NHCH2COOC2H5, and NHCH2CONHCH3, and the overall trends are considered in terms of the potential biomedical behavior of these compounds.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Inorganic Chemistry