Nanosecond laser flash photolytic generation and lifetimes in solvolytic media of diarylmethyl and p-methoxyphenethyl cations
Nanosecond laser flash photolytic generation and lifetimes in solvolytic media of diarylmethyl and p-methoxyphenethyl cations
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DOI：
10.1021/ja00228a066
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发表时间：
1988-09
影响因子：
15
通讯作者：
R. McCLELLAND;V. Kanagasabapathy;S. Steenken
中科院分区：
文献类型：
--
作者：
R. McCLELLAND;V. Kanagasabapathy;S. Steenken
虽然碳正离子是许多光化学反应的中间体，3闪光光解的证据有限，4它们的存在，这种技术直接研究这一重要类别的潜力尚未开发。本文报道的实验表明，标题仲阳离子在水和醇溶剂中均可观察到，并可直接测定它们与溶剂和叠氮离子的反应速率。我们还表明，至少在这里报道的例子中，基态阳离子的中间体的光溶剂化和烯烃的光质子化。二芳基甲基阳离子是通过光异裂解产生的，5以乙酸酯和对氰基苯基醚为前体。标准溶剂为20体积%乙腈：水（1：4 AN：W）和三氟乙醇（TFE）。如图1所示，通常观察到由阳离子和自由基引起的信号。阳离子，
Although carbocations are intermediates of a number of pho-tochemical reactions, 3 there has been only limited evidence4 from flash photolysis for their presence, and the potential of this technique for directly studying this important class has not been exploited. We report here experiments showing that the title secondary cations can beobserved in aqueous and alcohol solvents, and the rates of their reactions with solvent and azide ion directly measured. We also demonstrate that, at least in the examples reported here, ground-state cations are intermediates of both photosolvolyses and alkene photoprotonations. The diarylmethyl cations were produced by photoheterolysis, 5 with acetates and p-cyanophenyl ethers as precursors. Standard solvents were 20% by volumeacetonitrile: water (1: 4 AN: W) and trifluoroethanol (TFE). As illustrated in Figure 1, signals due to both cation and radical were typically observed. The cations,