Collect. Czech. Chem. Commun.
2009, 74, 43-55
https://doi.org/10.1135/cccc2008164
Published online 2009-01-20 10:11:08
Evidence for general base catalysis by protic solvents in a kinetic study of alcoholyses and hydrolyses of 1-(phenoxycarbonyl)pyridinium ions under both solvolytic and non-solvolytic conditions
Dennis N. Kevilla,*, Byoung-Chun Parka and Jin Burm Kyongb
a Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL 60115-2862, USA
b Department of Chemistry and Applied Chemistry, Hanyang University, Ansan-si, Gyeonggi-do 426-791, Korea
Abstract
The kinetics of nucleophilic substitution reactions of 1-(phenoxycarbonyl)pyridinium ions, prepared with the essentially non-nucleophilic/non-basic fluoroborate as the counterion, have been studied using up to 1.60 M methanol in acetonitrile as solvent and under solvolytic conditions in 2,2,2-trifluoroethan-1-ol (TFE) and its mixtures with water. Under the non- solvolytic conditions, the parent and three pyridine-ring-substituted derivatives were studied. Both second-order (first-order in methanol) and third-order (second-order in methanol) kinetic contributions were observed. In the solvolysis studies, since solvent ionizing power values were almost constant over the range of aqueous TFE studied, a Grunwald–Winstein equation treatment of the specific rates of solvolysis for the parent and the 4-methoxy derivative could be carried out in terms of variations in solvent nucleophilicity, and an appreciable sensitivity to changes in solvent nucleophilicity was found.
Keywords: Phenoxycarbonylpyridinium ions; Solvolysis; Alcoholysis; Kinetics; Grunwald–Winstein equation.
References: 50 live references.
