Atomic Tunneling in Organic Reactions

有机反应中的原子隧道

• 批准号: 08240101
• 负责人: ICHIKAWA Tsuneki
• 金额: $ 61.06万
• 依托单位: Hokkaido University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research on Priority Areas
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-08240101/
• 关键词: Atomic tunneling; Cryogenic chemistry; Cosmic chemistry; Hydrogen transfer; Hydrogen Addition; Hydrogen abstraction; Carbene; Radical; 原子トンネリング; 水素原子移動; マトリックスアイソレーション; 不斉合成; フリーラジカル; 低温化学反応; 同位体効果; 水素移行反応; 宇宙化学反応; アルキルラジカル; 星間塵; 錯体触媒

For elucidating the mechanism of inter- and intra-molecular tunneling of hydrogen atoms, hydrogen-atom abstraction, addition and exchange in organic systems have been studied between the temperature range of 10 K to 290 K by means of ESR, IR, mass spectroscopy, and product analyses. The results are summarized as follows ;1) Quantum-mechanical tunneling of hydrogen atoms is the measure process of chemical reaction at low temperatures, since the probability of the thermal activation of reaction systems is negligible with respect to the tunneling probability.2) The rate of tunneling depends exponentially on the area of tunneling barriers and the effective mass of tunneling particles. The rate strongly depends on the viscosity of the surroundings, if the deformation of, not only a tunneling particle, but also the other atoms in a reaction system are necessary during the optimum tunneling process. The surroundings with high viscosity prevent the deformation of the reaction-system for the op … More timum tunneling so that the tunneling barrier increases.3) The tunneling of hydrogen atoms plays a significant role in cosmic chemistry. The rate of the tunneling generally increases in the order of abstraction, addition to double bonds, and addition to free radicals. Ethane is only the product by hydrogen atom spray to the cryogenic thin film of ethylene, since the ethyl radicals generated by hydrogen-atom addition successively react with hydrogen atoms. The efficiency of the hydrogen-atom addition increases with decreasing temperature, since the slowing down of the diffusion of hydrogen atoms causes the increase of the reaction time for the tunneling.4) The shapes of the tunneling barriers for the intramolecular transfer of hydrogen atoms in carbene and nitrene strongly depend on the electronic configurations and the energy differences between the singlet and the triplet states.5) Hydrogen-atom tunneling does not play a significant role at ambient temperature in asymmetric syntheses by BINAP/Ru-catalyzed hydrogenation. Less

为了阐明氢原子在分子间和分子内隧穿的机理，本文用ESR、IR、质谱和产物分析等方法研究了10 ~ 290 K温度范围内有机体系中氢原子的夺取、加成和交换反应。结果表明：1）氢原子的量子力学隧穿是低温化学反应的量度过程，因为反应体系的热激活几率相对于隧穿几率可以忽略不计; 2）隧穿速率与隧穿势垒的面积和隧穿粒子的有效质量呈指数关系.如果在最佳隧穿过程中，不仅隧穿粒子，而且反应系统中的其他原子的变形都是必要的，则速率强烈地依赖于周围环境的粘度。高粘度的环境阻碍了反应体系的变形， ...更多信息 3）氢原子的隧穿在宇宙化学中起着重要的作用。隧穿的速率通常以提取、添加到双键和添加到自由基的顺序增加。乙烷是氢原子喷射到乙烯低温薄膜上的产物，因为氢原子加成产生的乙基自由基依次与氢原子反应。氢原子添加的效率随着温度的降低而增加，由于氢原子扩散的减慢导致隧穿反应时间的增加。4）卡宾和氮烯中氢原子分子内转移的隧穿势垒的形状强烈地依赖于电子构型和单重态与三重态之间的能量差。5）氢-原子隧穿在室温下在BINAP/Ru催化氢化的不对称合成中不起重要作用。少

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