RING-OPENING REACTION OF 5-MEMBERED CYCLIC AMMONIUM SALT GROUPS AT THE END OF POLY(TETRAHYDROFURAN)

The ring-opening reaction of 1-methylpyrrolidinium salt groups located at the end of poly(tetrahydrofuran) (poly(THF)) segment was studied w ith a series of p-substituted benzoate, having either methoxy, methyl, chloro or nitro substituent as a counter-anion. At 100 degrees C, suc h p-substituted benzoate anions as having an electron-donating methoxy or methyl substituent caused a ring-opening reaction of pyrrolidinium salt end groups, while others having an electron-withdrawing chloro o r nitro substituent were poorly reactive to undergo the ring-opening o f the end groups. Accordingly, the pathway of this nucleophilic reacti on is primarily governed by the basicity, i.e., pK(a), of the correspo nding p-substituted benzoic acid. At 120 degrees C, on the other hand, the nucleophilic substitution reaction at the N-methyl position of th e pyrrolidinium salt end groups occurred predominantly. (C) 1998 Elsev ier Science B.V. All rights reserved.