˙OH radical-induced oxidation of chlorobenzene in aqueous solution in the absence and presence of oxygen
˙OH radical-induced oxidation of chlorobenzene in aqueous solution in the absence and presence of oxygen
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DOI：
10.1039/p29960001097
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发表时间：
1996
期刊：
影响因子：
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通讯作者：
G. Merga;H. Schuchmann;B. Rao;C. Sonntag
中科院分区：
文献类型：
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作者：
G. Merga;H. Schuchmann;B. Rao;C. Sonntag
本文研究了在N_2O水溶液[G（stecOH）= 5.8 × 10 ~（-7）mol J ~（-1）]中辐解产生的羟基自由基与氯苯的反应。在Fe（CN）63 -存在下，主要产物（括号中的G值以10-7 mol J-1为单位）是2-氯苯酚（2.5）、3-氯苯酚（1.25）和4-氯苯酚（1.75）。电导检测脉冲辐解（在不存在氧化剂的情况下）表明，（这发生在stecOH自由基加成在ipso-位置）只是一个非常小的过程（0.03），并得出结论，stecOH自由基加成到邻位：Meta：帕拉：异位的比例为1：0.5：0.7：0.5。< 0.01，即在帕拉和邻位上存在明显的进攻偏好，并且在ipso位上的加成存在相当大的空间位阻。在无氧化剂存在下，氯酚的产率较低[G（总氯酚）= 0.4 × 10-7 molJ-1]，二聚产物[双（羟基氯代环己二烯）]占优势。这些初级二聚体大多不稳定，在脱水条件下（pH = 1时加热可促进脱水），可发生重排反应，生成各种二氯联苯、氯羟基联苯和二羟基联苯异构体，在O2存在下，氯羟基环己二烯自由基（kforward= 2.6 × 108 dm ~ 3 mol ~（-1）s ~（-1）; kreverse= 5.5 × 104 s ~（-1））可逆地转化为相应的过氧自由基。在此平衡状态下发生两个反应（k产物形成= 1.1 × 103 s-1）：HO 2-消除导致氯酚的三种异构体[G（总氯酚）= 2.1 × 10-7 mol J-1]和内过氧化物结构的形成，内过氧化物结构又转化为过氧自由基，随后进行断裂。这些产品中的大多数（通过GC分析其数量超过30）不含氯[G（氯离子）= 3.3 × 10-7 mol J-1]，除了少数含有氯乙烯官能团。
The reaction of hydroxyl radicals, generated radiolytically in N2O-containing aqueous solutions [G(˙OH)≈ 5.8 × 10–7 mol J–1], with chlorobenzene has been studied. In the presence of Fe(CN)63 – the major products (G values in units of 10–7 mol J–1 in parentheses) are 2-chlorophenol (2.5), 3-chlorophenol (1.25) and 4-chlorophenol (1.75). Pulse radiolysis with conductometric detection (in the absence of the oxidant) shows that prompt HCl formation (which occurs upon ˙OH radical addition at the ipso-position) is only a very minor process (0.03), and it is concluded that ˙OH radical addition to the ortho : meta : para : ipso positions occurs in a proportion of 1: 0.5 :0.7 : < 0.01, i.e. there is a noticeable preference of attack at the para and ortho positions and a considerable steric hindrance of the addition to the ipso position. In the absence of the oxidant, the yield of the chlorophenols is low [G(total chlorophenols)= 0.4 × 10–7 mol J–1] and dimeric products [bis(hydroxychlorocyclohexadienyls)] predominate. Most of these primary dimers are unstable and rearomatize under dehydration, which can be promoted by heating at pH 1, to various dichlorobiphenyl, chlorohydroxybiphenyl and dihydroxybiphenyl isomers.In the presence of O2, the chlorohydroxycyclohexadienyl radicals are (reversibly) converted into the corresponding peroxyl radicals (kforward= 2.6 × 108 dm3 mol–1 s–1; kreverse= 5.5 × 104 s–1). Out of this equilibrium two reactions occur (kproduct formation= 1.1 × 103 s–1): HO2-elimination leading to the three isomers of chlorophenol [G(chlorophenol total)= 2.1 × 10–7 mol J–1] and formation of endo-peroxidic structures which in turn are converted into peroxyl radicals and subsequently undergo fragmentation. Most of these products, which number in excess of 30 by GC analysis, are free of chlorine [G(chloride ion)= 3.3 × 10–7 mol J–1], apart from a few which contain the vinyl chloride function.