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首页> 外文期刊>Chemistry: A European journal >Double C-H activation of ethane by metal-free so_2~(*+) Radical cations
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Double C-H activation of ethane by metal-free so_2~(*+) Radical cations

机译：无金属的so_2〜（* +）自由基阳离子对乙烷的双重C-H活化

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The room-temperature C-H activation of ethane by metal-free SO _(2*+) radical cations has been investigated under different pressure regimes by mass spectrometric techniques. The major reaction channel is the conversion of ethane to ethylene accompanied by the formation of H_2SO_2~(*+), the radical cation of sulfoxylic acid. The mechanism of the double C-H activation, in the absence of the single activation product HSO_2~+, is elucidated by kinetic studies and quantum chemical calculations. Under near single-collision conditions the reaction occurs with rate constant k= 1.0 ×10-9 (±30%) Cm ~3S~(-1) molecule~(-1), efficiency = 90%, kinetic isotope effect kH/k_D = 1.1, and partial H/D scrambling. The theoretical analysis shows that the interaction of SO_2~(*+) with ethane through an oxygen atom directly leads to the C-H activation intermediate. The interaction through sulfur leads to an encounter complex that rapidly converts to the same intermediate. The double C-H activation occurs by a reaction path that lies below the reactants and involves intermediates separated by very low energy barriers, which include a complex of the ethyl cation suitable to undergo H/D scrambling. Key issues in the observed reactivity are electrontransfer processes, in which a crucial role is played by geometrical constraints. The work shows how mechanistic details disclosed by the reactions of metal-free electrophiles may contribute to the current understanding of the C-H activation of ethane.
机译：通过质谱技术研究了在不同压力下，室温下无金属的SO_（2 * +）自由基对乙烷的C-H活化作用。主要的反应通道是乙烷向乙烯的转化，伴随着亚硫酸的自由基阳离子H_2SO_2〜（* +）的形成。通过动力学研究和量子化学计算阐明了在没有单一活化产物HSO_2〜+的情况下双重C-H活化的机理。在接近单碰撞的条件下，反应发生的速率常数k = 1.0×10-9（±30％）Cm〜3S〜（-1）分子〜（-1），效率= 90％，动力学同位素效应kH / k_D = 1.1，并进行部分H / D加扰。理论分析表明，SO_2〜（* +）与乙烷通过氧原子的相互作用直接导致了C-H活化中间体。通过硫的相互作用导致相遇复合物迅速转化为相同的中间体。两次C-H活化是通过位于反应物下方的反应路径发生的，并且涉及被非常低的能垒隔开的中间体，其中所述能垒包括适合于进行H / D加扰的乙基阳离子络合物。观察到的反应性的关键问题是电子转移过程，其中几何约束起着至关重要的作用。这项工作表明，无金属亲电试剂反应所揭示的机理细节如何有助于当前对乙烷C-H活化的理解。

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