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Reactions of 1,ω‐bis(2‐bromopyridinium)alkanes with hydroxide ion in aqueous solutions
Author(s) -
Fernandez Carmen,
Toscano Vicente G.,
Chaimovich Hernan,
Politi Mario J.,
Hioka Noboru
Publication year - 1998
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/(sici)1099-1395(199801)11:1<25::aid-poc962>3.0.co;2-e
Subject(s) - chemistry , alkane , aqueous solution , methylene , kinetic isotope effect , propane , hydroxide , octane , butane , pentane , deuterium , ion , hexane , inorganic chemistry , medicinal chemistry , hydrocarbon , organic chemistry , catalysis , physics , quantum mechanics
The reaction of OH − ion with 1,ω‐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 − attack on premicellar aggregated N ‐alkylpyridinium compounds. 1,ω‐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 − ion fitted two consecutive first‐order reactions. The intermediate products, 1‐(2‐pyridone)‐ω‐(2‐bromopyridinium)alkane, and also the final products 1,ω‐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 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 − attack in premicellar aggregates. © 1998 John Wiley & Sons, Ltd.