Stereodynamics of chlorine atom reactions with organic molecules.
Stereodynamics of chlorine atom reactions with organic molecules.
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氯原子与有机分子反应的立体动力学。
DOI：
10.1021/jp054627l
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
A. Orr
中科院分区：
文献类型：
--
作者：
C. Murray;J. Pearce;S. Rudić;Bertrand Retail;A. Orr
最近的一系列实验和计算研究已经探索了从有机分子中提取氢的动力学如何受到分子中官能团的存在和基本结构基序（如应变环系统）的影响。比较了Cl原子与烷烃如乙烷的反应，Cl + CH_3CH_3-> HCl + CH_3CH_2（作为基准体系）和与官能化分子如醇、胺和卤代烷的反应，Cl + CH_3X-> HCl + CH_2X（X = OH、NH_2、卤素等）。揭示了大量的机械细节。虽然散射动力学，从测量的角分布的速度的HCl与量子态分辨率，显示出许多相似之处，大大增强的旋转激发的HCl产品观察到从反应的官能化分子。HCl的旋转激发程度与CH 2X自由基的偶极矩相关，因此至少部分归因于分离的极性反应产物之间的后过渡态偶极-偶极相互作用。这种解释是支持的直接动力学轨迹计算的飞行，因此，认为盐酸旋转作为一个原位探针的角各向异性的反应势能面在后过渡态区域。二甲醚和三，四元环化合物环氧乙烷（C-C2 H4 O）和氧杂环丁烷（C-C3 H6 O）的反应动力学之间的比较提出了问题的反应产物的重定向的作用在一个时间尺度上与它们的分离相称。因此，多原子分子的形状和结构被证明对这些直接抽象反应的立体动力学具有重要的影响。
A series of recent experimental and computational studies has explored how the dynamics of hydrogen abstraction from organic molecules are affected by the presence of functional groups in the molecule and by basic structural motifs such as strained ring systems. Comparisons drawn between reactions of Cl atoms with alkanes such as ethane, Cl + CH3CH3--> HCl + CH3CH2, which serve as benchmark systems, and with functionalized molecules such as alcohols, amines, and alkyl halides, Cl + CH3X --> HCl + CH2X (X = OH, NH2, halogen, etc.) expose a wealth of mechanistic detail. Although the scattering dynamics, as revealed from measured angular distributions of the velocities of the HCl with quantum-state resolution, show many similarities, much-enhanced rotational excitation of the HCl products is observed from reactions of the functionalized molecules. The degree of rotational excitation of the HCl correlates with the dipole moment of the CH2X radical and is thus attributed, at least in part, to post-transition-state dipole-dipole interactions between the separating, polar reaction products. This interpretation is supported by direct dynamics trajectories computed on-the-fly, and the HCl rotation is thus argued to serve as an in situ probe of the angular anisotropy of the reaction potential energy surface in the post-transition-state region. Comparisons between the dynamics of reactions of dimethyl ether and the three- and four-membered-ring compounds oxirane (c-C2H4O) and oxetane (c-C3H6O) raise questions about the role of reorientation of the reaction products on a time scale commensurate with their separation. The shapes and structures of polyatomic molecules are thus demonstrated to have important consequences for the stereodynamics of these direct abstraction reactions.