Nitration of phenols in reversed micelle systems and enhanced oxidation ability of dilute nitric acid (less than 2.0 molarity) in concentrated salt solutions

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• 作者：Masashi  ; Hojo ;   ; ^a ;   ; ^{mhojo@kochi-u.ac.jp} ; Ryosuke  ; Kato^a ; Akio  ; Narutaki^a ; Tetsuya  ; Maeda^a ; Yuki  ; Uji-yie^a
• 关键词：Nitryl or nitronium ion ; CTAC ; Evolution of chlorine ; Oxidation of bromide ; Salt effect ; Bulk water structure
• 刊名：Journal of Molecular Liquids
• 出版年：2011
• 出版时间：15 October 2011
• 年：2011
• 卷：163
• 期：3
• 页码：161-169
• 全文大小：725 K

文摘

In a previous paper, we have reported that dilute nitric acid in reversed micelle systems can oxidize the Br^{?/sup> ion to Br₂ and proposed that the nitryl (or nitronium) ion NO₂+ should be the active species in the oxidation process. Nitration of phenol in reversed micelle systems with dilute nitric acid, CHCl₃/CTAC/H₂O (2.0 mol dm?3 HNO₃ in the 1.0 % (v/v) H₂O phase), was performed at 35 ¡ãC to obtain 2- and 4-nitrophenols, where CTAC represents cetyltrimethylammonium chloride. In similar CTAC and AOT reversed micelle (CHCl₃ or heptane/AOT) systems, 4-methylphenol was converted to 2-nitro-4-methylphenol, where AOT stands for sodium bis(2-ethylhexyl) sulfosuccinate. In aqueous 2.0 mol dm?3 HNO₃ solution accompanied by 4.0 mol dm?3 LiCl (and a small amount of LiBr as the bromide resource), trans-1,4-dibromo-2-butene was successfully brominated to 1,2,3,4-tetrabromobutane. This result is a good evidence that the Br?/sup> ion can be oxidized to Br₂ in dilute nitric acid (2.0 mol dm?3) provided that it contains concentrated salts. At 20?0 ¡ãC, the apparent oxidation-reaction rate constants (k/s?1) of Br?/sup> to Br₂ were evaluated in 0.1?.0 mol dm?3 HNO₃ solution accompanied by concentrated LiCl (3.5?.0 mol dm?3). For chloride salts, the cation effects increased as Et₄N+ ?Na+ < Li+ < Ca2+ < Mg2+. Even the evolution of Cl₂ was demonstrated from < 2.0 mol dm?3 HNO₃ solution containing concentrated LiCl, MgCl₂, and CaCl₂ as well as AlCl₃, therefore, an indirect oxidation mechanism of the Br?/sup> ion through Cl₂ was proposed as follows: 2Cl?/sup> + NO₂+ ?Cl₂ + NO₂?/sup>; 2Br?/sup> + Cl₂ ?Br₂ + 2Cl?/sup>.}