ON THE MECHANISM OF OXIDATION OF HYDROXYCYCLOHEXADIENYL RADICALS WITH MOLECULAR OXYGEN
ON THE MECHANISM OF OXIDATION OF HYDROXYCYCLOHEXADIENYL RADICALS WITH MOLECULAR OXYGEN
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羟基环己二烯基自由基与分子氧的氧化机理研究
DOI：
10.1002/chin.198312127
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发表时间：
1982
期刊：
影响因子：
--
通讯作者：
T. Tezuka
中科院分区：
文献类型：
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作者：
N. Narita;T. Tezuka
0 反应进行两次，硅烷化后通过GC/质谱分析 18 0 含量。 b m/e 表示三甲基甲硅烷基醚。在 20°C 下通过 Pyrex 过滤器加热 3 小时。通过 GC/质谱测量了由该反应形成的 180 中甲酚、间甲酚和对甲酚的含量，表明有相当量的 1SO 掺入到甲苯中（表 I）。将间甲酚、间甲酚和对甲酚的混合物的甲苯溶液（10“2M）在1802下光解的对照表明甲酚90％以上的氧不受1802的影响。通过减去对照值和自然丰度进行校正，得到180间甲酚、间甲酚和对甲酚的净含量分别为14％、19％和19％，发现该反应中甲酚的邻位：间位：对位异构体比例为 51:25:24，与在通入氧气（44:40:16）或在氩气（71:9:20）下与 3.10 的反应中观察到的比例不同。当 3 在 1802 下在苯中光化学分解时，相当数量的 180 也被引入到苯中，得到 [l80] 苯酚（表 I）。与 3.4Several 反应相比，在氧气下，苯酚的产率（甲酚除外（7-10%）增加了一倍多）（苯酚从约 20% 到 50%）。这些观察结果表明，180 掺入芳族化合物表明，羟基环己二烯基自由基 (4) 与分子氧的氧化反应途径不同，我们认为 [180] 苯酚 (9a) 的形成可以通过二氢二醇机理来解释（方案 III），其中 4a 由苯和羟基自由基形成。与1802反应得到过氧自由基5a和/或6a，其通过以下方式塌缩成二氢二醇7a和/或8a
0 The reaction was carried out twice, and the 18 0 contents were analyzed by GC/mass spectra after silyation. b m/e for trimethyl-silyl ether. lamp through a Pyrex filter for 3 h at 20 C. The 180 contents in-, m-, and p-cresols formed by this reaction were measured by means of the GC/mass spectrum, revealing that an appreciable amount of lsO was incorporated into toluene (Table I). The control in which a toluene solution of a mixture of-, m-, and p-cresols (10 “2 M) was photolyzed under 1802 indicated that more than 90% of the oxygen of cresol was not affected by 1802. The correction by subtracting the control values and natural abundance gave the net contents of 180 in-, m-, and p-cresols as 14%, 19%, and 19%, respecitvely (TableI). The ortho: meta: para isomer ratio of cresol in this reaction was found to be 51: 25: 24, differing from the ratio observed under bubbling through oxygen (44: 40: 16) or under argon (71: 9: 20) in the reaction with 3.10 It is evident, therefore, that the incorporation of lsO in toluene accompanies the variationof the isomer ratio of cresol. A considerable amount of 180 was also incorporated in benzene to give [l80] phenol, when 3 was decomposed photochemically in benzene under 1802 (Table I). The yields of phenols, except for cresol (7-10%), more than doubled under oxygen compared with that underargon (from ca. 20% to 50% for phenol) in the reaction with 3.4Several mechanistic implications arise from these observations. The incorporation of the 180 into aromatics indicates that a re-action path (s) other than that proposed by Dorfman et al. 2 is involved in the oxidation of hydroxycyclohexadienyl radical (4) with molecularoxygen. We consider that the formation of [180] phenol (9a) can be accounted for bythe dihydrodiol mechanism (Scheme III), in which 4a formed from benzene and hydroxyl radical reacts with 1802 to give the peroxy radical 5a and/or 6a that collapses to the dihydrodiol 7a and/or 8a by the