Side-group-exchange reactions have been studied for short-chain linear oligomeric phosphazenes, (RO) 4P[N=P(OR 2)] nOR (n = 6, 10, 20, and 40) as models for the corresponding linear high polymers (n ∼ 15000). Specifically, the exchange behavior of oligomers where OR = OCH 2CF 3, OC 6H 5, OC 6H 4CHO-p, OC 6H 4CN-p, and OC 6H 4NO 2-p with sodium trifluoroethoxide was examined. The ease of aryloxy group replacement by trifluoroethoxy increased with the electron-withdrawing character in the order OR = OC 6H 5 ≪ OC 6H 4CHO-p < OC 6H 4CN-p < OC 6H 4NO 2-p, but the reaction was efficient only if the phosphazene contained no more than 20 repeating units. However, attempts to force slower reactions by the use of excess sodium trifluoroethoxide induced secondary reactions at the trifluoroethoxy units already introduced to produce CF 3CH 2OCH 2CF 3 and generate -O -Na + units in their place. The longest chain model underwent side-group-exchange reactions preferentially at the end units. These results are significant for the synthesis of phosphazene high polymers with fluoroalkoxy and aryloxy side groups.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Inorganic Chemistry