FREE-RADICAL REACTIONS OF CYCLIC ETHERS AND SULFIDES WITH BROMOTRICHLOROMETHANE
FREE-RADICAL REACTIONS OF CYCLIC ETHERS AND SULFIDES WITH BROMOTRICHLOROMETHANE
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DOI：
10.1002/poc.610020502
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发表时间：
1989-07-01
影响因子：
1.8
通讯作者：
CLAPP, GE
中科院分区：
文献类型：
--
作者：
HALLEN, RT;GLEICHER, GJ;CLAPP, GE
在70°C下测定了一系列十二种饱和环醚和硫化物的氢原子提取相对速率。提取自由基可由溴三氯甲烷光解或由AIBN热分解产生。反应速率没有表现出依赖于自由基生成的方法。反应仅在与杂原子相邻的位置发生。环醚的反应活性顺序为C_4H_8O> C_6H_1_2O> C_3H_6O> C_5H_10O。这种趋势表明环应变的明显影响，然而，四氢呋喃相对于氧杂环庚烷的反应性略高表明立体电子因素也有贡献。环硫醚的反应性比相应的醚快，其顺序为C_4H_8S> C_5H_10S> C_6H_12S。这意味着环应变的影响很小。主要的结构效应是硫原子的可变供电子能力。还测定了硫杂环丁烷的反应速率。它被发现优先进行SH2攻击的硫原子，然后开环，而不是氢提取。这两个系列的化合物的反应性降低的诱导效应的第二个杂原子β的reaciton网站。
The relative rates of hydrogen atom abstraction from a series of twelve saturated cyclic ethers and sulfides were determined at 70°C. The abstracting radical could be generated from bromotrichloromethane both photolytically or by the thermal decomposition of AIBN. The reaction rates did not show a dependence upon method of radical generation. Reaction occurred only at the position adjacent to the heteroatom. The reactivity of the cyclic ethers was in the order C4H8O > C6H12O > C3H6O > C5H10O. This trend would indicate appreciable influence by ring strain, however, the slightly greater reactivity of tetrahydrofuran relative to oxepane suggests a contribution by stereoelectronic factors as well. The reactivity of the cyclic sulfides, which reacted faster than the corresponding ethers, was in the order C4H8S > C5H10S > C6H12S. This would imply little influence of ring strain. The major structural effect would be that of variable electron donating ability of the sulfur atom. The rate of reaction of thietane was also determined. It was found to preferentially undergo SH2 attack at the sulfur atom followed by ring opening rather than hydrogen abstraction. The reactivities of both series of compounds were decreased by the inductive effect of a second heteroatom beta to the reaciton site.