Reactions of aromatic radical anions. 12. Kinetic studies of the reaction of radical anions of varying reduction potential with n-hexyl bromides, iodides, and chlorides
Reactions of aromatic radical anions. 12. Kinetic studies of the reaction of radical anions of varying reduction potential with n-hexyl bromides, iodides, and chlorides
复制标题
芳香族自由基阴离子的反应。
DOI：
10.1021/ja00440a048
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发表时间：
1976
期刊：
影响因子：
--
通讯作者：
D. Juckett
中科院分区：
文献类型：
--
作者：
S. Bank;D. Juckett
测定了还原电势系列扩展的芳香族自由基阴离子还原碘化物、溴化物和氯化物的二级速率常数。该系列化合物包括联苯(-E I，2.80 V)、石脑油-烯(-GB 1/2，2.60 V)、芘(-GB 1/2，2.10 V)、菲(-GB 1/2，1.98 V)、荧菲(-GB 1/2，1.77 V)和茂(-GB 1/2，1.67 V)。反应速率的对数与阴离子的还原电势之间不是线性关系。类似地，在芳香族自由基阴离子恒定时，速率的对数与卤素的碳-卤键强度加上电子亲和力之间的关系不是线性的。考虑了结构变化和离子对对反应速率的影响。这些模式表明从高放热反应到低放热反应过渡态的位置发生了变化。考虑了有机卤代阴离子中间体的可能性。讨论了这项工作与电化学还原和格氏形成的关系。芳香族自由基阴离子，如萘钠，为烷基卤化物的还原提供了一条低能量的途径，这一点已被人们所知。1从机械论的观点来看，这种反应引起了相当大的兴趣，2最近，动力学研究对我们的理解做出了贡献。3-5我们之前对反应的动力学研究
The second-order rate constants for the reduction of «-hexyl iodides, bromides, and chlorides by aromatic radical an-ions of an expanded reduction potential series have been determined. The series includes biphenyl (—E\¡ i, 2.80 V), naphtha-lene (—£ 1/2, 2.60 V), pyrene (—£ 1/2, 2.10 V), anthracene (—£ 1/2, 1.98 V), fluoranthene (-£ 1/2, 1.77 V), and perylene (-£ 1/2, 1.67 V). The relationship between the log of the rates and the reduction potentials of the radical anions at constant ha-lide is not linear. Similarly, the relationship between the log of the rates and the carbon-halogen bond strength plus electron affinity of the halogen at constant aromatic radical anion is not linear. The effects of structural variationsand of ion pairing on the reaction rates are considered. These patterns indicate changes in the position of the transition state in going from a high-ly exothermicto a less exothermic reaction. The possibility of an organic halide radical anion intermediate is considered. The relationship between this work and electrochemical reduction and Grignard formation is discussed.It has been known for some time that aromatic radical an-ions, such as sodium naphthalene, provide a low-energy pathway for the reduction of alkyl halides. 1 This reaction has elicited considerable interest from a mechanistic point of view, 2 and more recently, kinetic studieshave contributed to our understanding. 3-5 Our previous kinetic study of the reactions