Rate Constants for Reactions of Alkyl Radicals with Water and Methanol Complexes of Triethylborane
作者:Jing Jin、Martin Newcomb
DOI:10.1021/jo070336s
日期:2007.7.1
Reactions of secondaryalkyl radicals with triethylborane and several of its complexes were studied. The H-atom transfer reactions from Et3B−OH2 and Et3B−OD2 were suppressed by addition of pyridine to the reaction mixture. Rate constants for reactions of secondaryalkyl radicals with triethylborane and its complexes with water, deuterium oxide, methanol, and THF at ambient temperature were determined
研究了仲烷基与三乙基硼烷及其几种配合物的反应。来自Et 3 B-OH 2和Et 3 B-OD 2的H原子转移反应通过向反应混合物中加入吡啶来抑制H 2 O 3。通过自由基钟法确定了在室温下仲烷基与三乙基硼烷及其与水,氧化氘,甲醇和THF的配合物反应的速率常数。评价1-十一烷基-5-己烯基的环化和1-环丁基十二烷基的开环作为时钟反应。环丁基羰基自由基开环具有合适的速度,可以相对精确地确定H原子转移俘获和重排的速率常数的比率,这些比率与环丁基羰基自由基开环的估计速率常数相结合,得出速率常数的绝对值用于H原子转移反应。例如,4 M - 1 s - 1。用甲苯中的Et 3 B-CH 3 OH络合物进行的可变温度研究表明,氢原子转移反应具有异常高的熵需求,这导致与自由基开环和环化反应在降低的竞争下竞争,氢原子转移捕获反应的效率大大提高温度。