Activation of Dioxygen Mediated by Metal Ions, and Synthetic Application.

本工作的主要目的是建立一种一步氧化苯制酚的合成方法。在早期的工作中，我们报道了Cu^+离子可以激活分子氧。当系统中存在苯时，就会产生苯酚和对苯二酚。初级步骤估计为用方程表示的反应。(1)-(3)，但大多数机械细节都是模棱两可的。cu ^+ + O_2 + 2H^+ -> 2Cu^<2+> + H_2O_2 (1)；Cu^+ + H_2O_2 + H^+ -> Cu^<2+> + OH + H_2O (2)；本文讨论了铜(1)离子催化空气氧化苯的机理及合成可行性。结论如下：1。(机制)。(1)通过动力学研究，确定活性物质为OH；(2)失活发生在OH或H_2O_2阶段；(3) H_2O_2生产效率是定量的；(4) H_2O_2的生成速率远大于分解速率。[与其他系统的比较]。o -示踪实验表明，羟基-环己二烯及其过氧自由基是中间体。对苯二酚的生成是本体系的特征，这在其他体系中从未观察到，如芬顿反应。(合成可行性)。苯酚与对苯二酚的相对比值强烈依赖于溶液的ph值。前者在较低的ph值下占主导地位（<3），后者在较高的ph值下占主导地位（>.3）。在pH为3的条件下对Cu^+进行连续萃取和电解再生，得到的对苯醌的电流效率为50%。本系统具有若干优点，具有综合可行性。即(1)不需要过氧化氢；(2)反应有效、温和；(3)选择性地得到苯酚或对苯二酚。

The main object of this work is placed on developing a synthetic method for one-step oxidation of benzene to phenols. In earlier works, we reported that Cu^+ ions can activate molecular xoygen. When benzene is present in the system, both phenol and hydroquinone are produced. The primary steps are estimated to be the reactions expressed by eqs. (1)-(3), but most of mechanistic details were left ambiguous.iCu^+ + O_2 + 2H^+ -> 2Cu^<2+> + H_2O_2 (1) ; Cu^+ + H_2O_2 + H^+ -> Cu^<2+> + OH + H_2O (2) ;OH + C_6H_6 -----> C_6H_5OH (3)In this work, mechanistic detail and synthetic feasibility of air oxidation of benzene catalyzed by Copper(1) ions were discussed. Conclusions are as follows.1. [Mechanism]. (1) By kinetic study, it is confirmed that active species is OH; (2) Deactivation occurs at the stage of OH or H_2O_2; (3) Efficiency for H_2O_2 production is quantitative; (4) The formation rate of H_2O_2 is much gaster than the decomposition rate.2. [Comparison with Other Systems]. ^<18>O-Tracer experiment indicates that hydroxy- cyclohexadienyl and its peroxy radicals are the intermediates. The formation of hydroquinone is characteristic feature of the present system, which is never observed in the other systems, such as the Fenton's reaction.3. [Synthetic Feasibility]. The relative ratio of phenol to hydroquinone strongly depends on solution pH. The former dominates at lower pHs (<3), and the latter at higher pHs (>3). When both continuous extraction and electrolytic regeneration of Cu^+ were applied to the system at pH 3, p-benzoquinone was obtained in a 50% current efficiency.The present system has several merits and, therefore, provides much synthetic feasibility. Namely, (1) Hydrogen peroxide is unnecessary; (2) The reaction is effective and mild; (3) Either phenol or hydroquinone is obtained selectively.