Fluxional exchange of tert-butyllithium tetramers from temperature-dependent carbon-13-lithium-6 coupling
Fluxional exchange of tert-butyllithium tetramers from temperature-dependent carbon-13-lithium-6 coupling
复制标题
温度依赖性碳 13 锂 6 偶联产生叔丁基锂四聚体的流动交换
DOI：
10.1021/om00140a016
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发表时间：
1986
期刊：
影响因子：
2.8
通讯作者：
T. Young
中科院分区：
文献类型：
--
作者：
Ruthanne D. Thomas;Matthew T. Clarke;R. Jensen;T. Young
对叔丁基和叔戊基锂-6Li在环戊烷溶液中的~（13）C和~ 6Li NMR谱进行了研究。叔丁基锂-6Li的碳原子的质子去耦13 C共振从-5 C以上的尖锐九线多重峰，J（13 C-6Li）= 4.1 Hz变化到-22 C以下的尖锐七线多重峰，J（13 C-6Li）= 5.4 Hz。这表明叔丁基锂四聚体在低温下的流动交换减慢。的13 C和6Li交换增宽光谱的线形分析产生的流动交换的活化参数为 *= 25.0 0。1 kcal/mol，AS*= 44 × 1eu。与此相反，铁戊基锂-6Li的碳是一个温度无关的九线多重峰，c/（13 C-6Li）= 4.0 Hz。这可以用AG*（188 K）< 7.9 kcal/mol的类似流动过程来解释。讨论了可能的流动交换机制。
13C and 6Li NMR studies have been carried out on tert-butyl-and tert-pentyllithium-6Lŋ in cyclopentane solution. The proton-decoupled 13C resonance for the-carbon of íerf-butyllithium-6Lŋ varies from a sharp nine-line multiplet above-5 C, J (13C-6Li)= 4.1 Hz, to a sharp seven-line multiplet below-22 C, J (13C-6Li)= 5.4 Hz. This indicates slowing of the fluxional exchange of the ieri-butyllithium tetramer at low temperatures. A line-shape analysis of the 13C and 6Li exchange-broadened spectra yields activation parameters for the fluxional exchange of*= 25.0 ą0. 1 kcal/mol and AS*= 44 ą 1 eu. In contrast, the-carbon of feri-pentyllithium-6Li is a temperature-independent nine-line multiplet with c/(13C-6Li)= 4.0 Hz. This is interpreted in terms of a similar fluxional process with AG*(188 K)< 7.9 kcal/mol. The possible mechanisms for fluxional exchange are discussed.