Photohydration of styrenes and phenylacetylenes. General acid catalysis and Broensted relationships
Photohydration of styrenes and phenylacetylenes. General acid catalysis and Broensted relationships
复制标题
苯乙烯和苯乙炔的光水合。
DOI：
--
复制
发表时间：
1987
期刊：
影响因子：
--
通讯作者：
K. Yates
中科院分区：
文献类型：
--
作者：
J. Mcewen;K. Yates
在缓冲溶液中，研究了一系列取代苯乙烯酸催化的光水化反应。在一系列催化剂的情况下，在5个案例中清楚地检测到一般的酸催化，并且近似线性的Broensted图给出了.帽α.取值范围在0.14-0.18之间。通过与10/SUP 11/-10/SUP 15/范围的热水化数据的比较，估计了从S/SUP0/到S/SUP1/的激发引起的速率增强。用多元回归分析处理一般酸催化的速率常数(k/subHA/)与缓冲液pk/subHA/值的关系，结果表明Broensted曲线是光滑的，正如Eigen和Marcus方程所预测的那样。然而，Broensted曲率的可靠数值还不能确定。用一系列硝基取代类似物考察了类似三重态可能的催化活性，但没有检测到一般的酸催化作用。讨论了在这些光反应中控制一般酸催化检测的因素。
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.