AROMATIC SUBSTITUTION .13. COMPARISON OF NITRIC ACID AND MIXED ACID NITRATION OF ALKYLBENZENES AND BENZENE WITH NITRONIUM SALT NITRATIONS
AROMATIC SUBSTITUTION .13. COMPARISON OF NITRIC ACID AND MIXED ACID NITRATION OF ALKYLBENZENES AND BENZENE WITH NITRONIUM SALT NITRATIONS
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DOI：
10.1021/ja00878a019
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发表时间：
1962-01-01
影响因子：
15
通讯作者：
KUHN, SJ
中科院分区：
文献类型：
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作者：
OLAH, GA;FLOOD, SH;KUHN, SJ
对烷基苯和苯在硝基甲烷、乙酸、乙酸酐、四亚甲基砜和硫酸溶液中的硝酸和混合酸硝化与硝鎓盐硝化进行了比较。在硫酸溶液或使用混合酸的浓缩有机溶液中，存在可检测量的 XO2+，硝化显示出低底物但高位置选择性，与之前用预先制备的 XO2+ 盐进行硝化的观察结果完全一致。在酸的稀有机溶液中，没有光谱（拉曼和红外）可检测到硝鎓离子的量，并且这些反应的缓慢动力学步骤必须被认为是NOT的形成。与芳香族底物的相互作用必须在硝鎓离子完全形成之前发生，并且其较弱的亲电子前体表现出更高的底物选择性。对 NOTBF·四亚甲基砜溶液的冷冻镜研究提供了非常有限的离子分离的证据。因此，有机溶剂中硝鎓盐的硝化不能被视为游离NOT离子与芳族化合物的相互作用，而是被认为是芳族化合物对溶剂化NOTBFT离子对的亲核置换。这种类型的相互作用与形成定向络合物类型活化态所需的大量活化能一致，如先前针对硝鎓盐硝化所建议的。
A comparison of nitric acid and mixed acid nitrations of alkylbenzenes and benzene in nitromethane, acetic acid, acetic anhydride, tetramethylene sulfone and sulfuric acid solutions with nitronium salt nitrations was carried out. In sulfuric acid solutions or in concentrated organic solutions using mixed acid, where detectable amounts of X02+ are present, nitrations show a low substrate but high positional selectivity, in complete agreement with previous observations of nitrations with preprepared X02+ salts. In dilute organic solutions of the acids there is no spectroscopically (Raman and infrared) detectable amount of nitronium ion and the slow kinetic step of these reactions must be considered to be the formation of NOT. The interaction with the aromatic substrate must be taking place even before the nitronium ion is completely formed and its weaker electrophile precursor shows higher substrate selectivity. Cryoscopic investigation of tetramethylene sulfone solutions of NOTBF·-gave evidence of very limited ion separation. Therefore, nitrations with nitronium salts in organic solvents cannot be considered as interaction of the free NOT ion with aromatics, but as nucleophilic displacement of the solvated NOTBFT ion pair by the aromatics. An interaction of this type is in accordance with substantial activation energy needed for the formation of an oriented-complex type activated state, suggested for nitronium salt nitrations previously.