REACTIONS OF 1,OMEGA-BIS(2-BROMOPYRIDINIUM)ALKANES WITH HYDROXIDE IONIN AQUEOUS-SOLUTIONS

The reaction of OH- ion with 1,omega-bis(2-bromopyridinium)alkanes, wh ere the reaction centers are separated by a varying number of methylen e groups, was investigated to model the increased velocity of OH- atta ck on premicellar aggregated N-alkylpyridinium compounds. 1,omega-Bis( 2-bromopyridinium)alkanes (RPBr) [R = propane (I), butane (II), pentan e (III), hexane (IV) and octane (V)] were synthesized and characterize d by standard procedures. The kinetics of I-V with OH- ion fitted two consecutive first-order reactions. The intermediate products, 1-(2-pyr idone)-omega-(2-bromopyridinium)alkane, and also the final products 1, omega-bis(2-pyridone)alkanes, were isolated. Deuterium isotope effects , activation parameters and salt effects on the reaction rates suggest that OH- attack is rate limiting and there is a through-space acceler ation of the initial attack due to the proximity of the positive charg es. These results place an upper limit of 20-fold for the electrostati c acceleration in OH- attack in premicellar aggregates. (C) 1998 John Wiley & Sons, Ltd.