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Photohydration of styrenes and phenylacetylenes. General acid catalysis and Broensted relationships

Journal Article · · J. Am. Chem. Soc.; (United States)
DOI:https://doi.org/10.1021/ja00253a035· OSTI ID:5953024
The acid-catalyzed photohydrations of a series of substituted styrenes and phenylacetylenes have been investigated in aqueous buffer solutions. General acid catalysis was clearly detected in five cases with a range of catalysts, and approximately linear Broensted plots gave ..cap alpha.. values in the range 0.14-0.18. The rate enhancements caused by excitation from S/sub 0/ to S/sub 1/ were estimated from comparisons with thermal hydration data to be in the 10/sup 11/-10/sup 15/ range. Treatment of the dependence of the rate constants for general acid catalysis (k/sub HA/) on the buffer pK/sub HA/ values with multiple regression analysis suggests that the Broensted plots are smoothly curved, as predicted by Eigen and by the Marcus equation. However, reliable values of the Broensted curvature could not be established. The possible catalytic reactivity of analogous triplet states was examined with a series of nitrosubstituted analogues, but no general acid catalysis could be detected. The factors controlling the detection of general acid catalysis in these photoreactions are discussed.
Research Organization:
Univ. of Toronto, Ontario
OSTI ID:
5953024
Journal Information:
J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:19; ISSN JACSA
Country of Publication:
United States
Language:
English