Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States.
J Am Chem Soc. 2016 Mar 30;138(12):4237-42. doi: 10.1021/jacs.6b01028. Epub 2016 Mar 22.
We report molecular dynamics simulations of the reaction of dimethyldioxirane (DMDO) with isobutane. The reaction involves hydrogen atom abstraction in the transition state, and trajectories branch to the oxygen rebound pathway, which gives tert-butanol and acetone, or a separated radical pair. In the gas phase, only 10% of the reactive trajectories undergo the oxygen rebound pathway, but this increases to 90% in simulations in an implicit acetone solvent (SMD) because the oxygen rebound becomes barrierless in solution. Short-lived diradical species were observed in the oxygen rebound trajectories. The time gap between C-H bond-breaking and C-O bond formation ranges from 30 to 150 fs, close to the <200 fs lifetime of radical pairs from DMDO hydroxylation of trans-1-phenyl-2-ethylcyclopropane measured by Newcomb.
我们报告了二甲基二环氧乙烷（DMDO）与异丁烷反应的分子动力学模拟。该反应涉及过渡态中的氢原子抽象，轨迹分支到氧回弹途径，生成叔丁醇和丙酮，或分离的自由基对。在气相中，只有 10%的反应轨迹经历氧回弹途径，但在包含隐式丙酮溶剂（SMD）的模拟中，这一比例增加到 90%，因为在溶液中氧回弹变得无势垒。在氧回弹轨迹中观察到了短寿命的双自由基物种。C-H 键断裂和 C-O 键形成之间的时间间隔范围为 30 至 150 fs，接近 Newcomb 测量的 DMDO 对反式-1-苯基-2-乙基环丙烷羟化的自由基对的 200 fs 寿命。
