Stabilities of trivalent carbon species. 5. Equilibriums of excited singlet alcohols and carbocations
Stabilities of trivalent carbon species. 5. Equilibriums of excited singlet alcohols and carbocations
复制标题
三价碳物种的稳定性。
DOI：
10.1021/jo01325a026
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发表时间：
1979
影响因子：
3.6
通讯作者：
N. Thame
中科院分区：
文献类型：
--
作者：
M. Feldman;N. Thame
荧光滴定进行了与四个醇，其大大增强的反应性，以形成碳正离子的激发单重态预测由福斯特循环计算。对5 H-二苯并[a，d]环庚三烯-5-醇的荧光滴定分析表明，该醇在+ 1和-3之间的Hr下以激发单重态而不是基态与酸反应。正如福斯特循环所预测的那样，在非常低的酸浓度下形成阳离子被激发的单线态醇的短寿命所排除。醇和相应阳离子的荧光强度的行为意味着在激发态反应中涉及另一种非荧光物质。阳离子的分解光解表明，其主要的光反应是氢转移和醚的形成。
Fluorescence titrations were carried out with four alcohols whose greatly enhanced reactivity to form carbocations in the excited singlet state is predicted by Forster cycle calculations. Analysis of the fluorescence titration of 5//-dibenzo [a, d] cycloheptatrien-5-ol indicates that the alcohol reacts with acid in the excited singlet state, but not the ground state, at Hr between+ 1 and-3. Formation of the cation at very low acid concentrations, as predicted by the Forster cycle, is precluded by the short lifetime of the excited singlet alcohol. The behavior of the fluores-cence intensities of the alcohol and corresponding cation implies the involvement of another, nonfluorescing species in the excited-state reactions. Preparative photolyses of the cation indicate that its principal photoreactions are hydride transfer and ether formation.