Rate and equilibrium studies of the reaction of oxyanions with 2-phenyloxazol-5(4H)-one
- 1 January 1986
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 1,p. 163-168
- https://doi.org/10.1039/p29860000163
Abstract
Equilibrium constants for the reaction of phenoxide ions with 2-phenyloxazol-5(4H)-one at 25 °C and 1 M ionic strength obey a Brønsted relationship (log kOH/kArO= log K′=–1.73pKArOH– 15.81) and are not subject to steric effects from ortho-substituents. Both forward and reverse rate parameters exhibit steric effects, and the Brønsted equations for meta- and para-substituted species are log kOH=–0.81 pKArOH+ 9.75, and log kArO= 0.95pKArOH– 6.40. There is no break in the Brønsted line in the region of pKArOH 5–11, consistent with a single transition-state. An upward deviation exists for oxyanions with low basicity (pKXOH < 5); one of these oxyanions, betaine, has a solvent deuterium oxide isotope effect for its reaction with the oxazolone greater than 2, consistent with a general base mechanism for attack for these species. The results for nucleophilic attack of phenolate anions are in agreement with a concerted displacement at the carbonyl group.Keywords
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