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首页> 外文期刊>Chemistry: A European journal >On the Gas-Phase Reactivity of Complexed OH~+ with Halogenated Alkanes
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On the Gas-Phase Reactivity of Complexed OH~+ with Halogenated Alkanes

机译：OH〜+与卤代烷烃的气相反应性研究

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摘要

OH~+ is an extraordinarily strong oxidant.Complexed forms(L- OH~+),such as H_2OOH~+,H_3NOH~+,or iron-porphyrin-OH~+ are the anticipated oxidants in many chemical reactions.While these molecules are typically not stable in solution,their isolation can be achieved in the gas phase.We report a systematic survey of the influence on L on the reactivity of L- OH~+ towards alkanes and halogenated alkanes,showing the tremendous influence of L on the reactivity of L-OH~+.With the help of with quantum chemical calculations,detailed mechanistic insights on these very general reactions are gained.The gas-phase pseudo-first-order reaction rates of H_2OOH~+,H_3NOH~+,and protonated 4-picoline-.N-oxide towards isobutane and different halogenated alkanes C_nH_2n+1Cl(n= 1-4),HCF_3,CF_4,and CF_2Cl_2 have been determined by means of Fourier transform ion cyclotron resonance meaurements.Reaction rates for H_2OOH~+ are generally fast(7.2 x 10~(-10)-3.0X 10~(-9)cm~3mol~(-1)s~(-1))and only in the cases HCF_3 and CF_4 no reactivity is observed.In contrast to this H_3NOH~+ only reacts with tC_4H_9Cl(k_(obs)= 9.2x10~(-10)),while 4-CH_3-C_5H_4N-OH~+ is completely unreactive.While H_2OOH~+ oxidizes alkanes by an initial hydride abstraction upon formation of a carbocation,it reacts with halogenated alkanes at the chlorine atom.Two mechanistic scenarios,namely oxidation at the halogen atom or proton transfer are found.Accurate proton affinities for HOOH,NH_2OH,a series of alkanes C_nH_(2n+2)(n = l-4),and halogenated alkanes C_nH_2n+1Cl(n = l-4),HCF_3,CF_4,and CF_2Cl_2,were calculated by using the G3 method and are in excellent agreement with experimental values,where available.The G3 enthalpies of reaction are also consistent with the observed products.The tendency for oxidation of alkanes by hydride abstraction is expressed in terms of G3 hydride affinities of the corresponding cationic products C_nH_2n+1(n = l-4)and C_nH_2nC1~+(n = l-4).The hypersur-face for the reaction of H_2OOH~+ with CH_3C1 and C_2H_5C1 was calculated at the B3LYP,MP2,and G3_m,level,underlining the three mechanistic scenarios in which the reaction is either induced by oxidation at the hydrogen or the halogen atom,or by proton transfer.
机译：OH〜+是一种非常强的氧化剂.H_2OOH〜+，H_3NOH〜+或铁卟啉-OH〜+等复杂形式（L- OH〜+）是许多化学反应中预期的氧化剂。通常在溶液中不稳定，可以在气相中实现分离。我们报告了对L对L- OH〜+对烷烃和卤代烷烃反应性的影响的系统调查，表明L对反应性的巨大影响借助量子化学计算，对这些非常笼统的反应获得了详细的力学见解.H_2OOH〜+，H_3NOH〜+和质子化的气相伪一级反应速率为4通过傅立叶变换离子回旋加速器共振法测定了对异丁烷和不同卤代烷烃C_nH_2n + 1Cl（n = 1-4），HCF_3，CF_4和CF_2Cl_2的-picoline-.N-氧化物.H_2OOH〜+的反应速率为仅在HCF_3情况下通常快（7.2 x 10〜（-10）-3.0X 10〜（-9）cm〜3mol〜（-1）s〜（-1））与此相反，H_3NOH〜+仅与tC_4H_9Cl（k_（obs）= 9.2x10〜（-10））反应，而4-CH_3-C_5H_4N-OH〜+则完全不反应，而H_2OOH〜 +在形成碳正离子时通过最初的氢化物抽象作用氧化烷烃，在氯原子上与卤代烷烃反应。发现了两种机理，即在卤素原子上氧化或质子转移。HOOH，NH_2OH的精确质子亲合力使用G3方法计算的烷烃C_nH_（2n + 2）（n = 1-4），卤代烷烃C_nH_2n + 1Cl（n = 1-4），HCF_3，CF_4和CF_2Cl_2的摩尔数与G3的反应焓也与观察到的产物一致。氢化物提取引起烷烃氧化的趋势表示为相应阳离子产物C_nH_2n + 1（n = l-4的G3氢化物亲和力） ）和C_nH_2nC1〜+（n = l-4）.H_2OOH〜+与CH_3C1反应的超表面C_2H_5C1是在B3LYP，MP2和G3_m的水平上计算的，强调了三种机制，在该情形下，反应是由氢或卤素原子上的氧化或质子转移引起的。

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