Aromatic nitration with ion radical pairs [ArH.cntdot.+,NO2.cntdot.] as reactive intermediates. Time-resolved studies of charge-transfer activation of dialkoxybenzenes
Aromatic nitration with ion radical pairs [ArH.cntdot.+,NO2.cntdot.] as reactive intermediates. Time-resolved studies of charge-transfer activation of dialkoxybenzenes
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离子自由基对的芳香硝化 [ArH.cntdot。
DOI：
10.1021/ja00251a032
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发表时间：
1987
影响因子：
15
通讯作者：
J. Kochi
中科院分区：
文献类型：
--
作者：
S. Sankararaman;W. Haney;J. Kochi
芳香族硝化进行亲电条件下，并通过电荷转移活化提供相同的产率和异构体分布的硝化产物从一个共同的系列芳香族醚（ArH）。时间分辨光谱确定电荷转移硝化通过离子自由基对（ArH/sup +/，NO/sub 2/）进行，该离子自由基对由电子给体-受体的有意激发产生。pi..芳烃与C（NO/sub 2/）/sub 4/的络合物。激光闪光光解的电荷转移带定义的芳烃阳离子自由基ArH/sup +/的演变，并允许其衰减动力学描绘在各种溶剂和添加的盐。研究了取代对二甲氧基苯CH/sub 3/OC/sub 6/H/sub 4/OCH/sub 2/X（X = CO/sub 2/H，CO/sub 2/sup -/，CO/sub 2/Et，CH/sub 2/OH）体系中ArH/sup +/的内捕集.的机制相关的崩溃（ArH/sup +/，NO/sub 2/）的Wheland中间体进行了讨论的情况下，亲电芳香族硝化。
Aromatic nitrations carried out both under electrophilic conditions and by charge-transfer activation afford the same yields and isomer distributions of nitration products from a common series of aromatic ethers (ArH). Time-resolved spectroscopy establishes the charge-transfer nitration to proceed via the ion radical pair (ArH/sup +/,NO/sub 2/), generated by the deliberate excitation of the electron donor-acceptor or ..pi.. complex of the arene with C(NO/sub 2/)/sub 4/. Laser flash photolysis of the charge-transfer band defines the evolution of the arene cation radical ArH/sup +/ and allows its decay kinetics to be delineated in various solvents and with added salts. The internal trapping of ArH/sup +/ is examined in the substituted p-dimethoxybenzenes CH/sub 3/OC/sub 6/H/sub 4/OCH/sub 2/X with X = CO/sub 2/H, CO/sub 2//sup -/, CO/sub 2/Et, and CH/sub 2/OH as the pendant functional groups. The mechanistic relevance of the collapse of (ArH/sup +/, NO/sub 2/) to the Wheland intermediate is discussed in the context of electrophilic aromatic nitrations.