Reactions of 1,ω-bis(2-bromopyridinium)alkanes with hydroxide ion in aqueous solutions

✍ Scribed by Carmen Fernandez; Vicente G. Toscano; Hernan Chaimovich; Mario J. Politi; Noboru Hioka

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 161 KB
• Volume: 11
• Category: Article
• ISSN: 0894-3230
• DOI: 10.1002/(sici)1099-1395(199801)11:1<25::aid-poc962>3.0.co;2-e

✦ Synopsis

The reaction of OH À ion with 1,o-bis(2-bromopyridinium)alkanes, where the reaction centers are separated by a varying number of methylene groups, was investigated to model the increased velocity of OH À attack on premicellar aggregated N-alkylpyridinium compounds. 1,o-Bis(2-bromopyridinium)alkanes (RPBr) [R = propane (I), butane (II), pentane (III), hexane (IV) and octane (V)] were synthesized and characterized by standard procedures. The kinetics of I-V with OH À ion fitted two consecutive first-order reactions. The intermediate products, 1-(2pyridone)-o-(2-bromopyridinium)alkane, and also the final products 1,o-bis(2-pyridone)alkanes, were isolated. Deuterium isotope effects, activation parameters and salt effects on the reaction rates suggest that OH À attack is rate limiting and there is a through-space acceleration of the initial attack due to the proximity of the positive charges. These results place an upper limit of 20-fold for the electrostatic acceleration in OH À attack in premicellar aggregates.