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应用微型反应-色谱技术(稳态流动技术及脉冲技术)研究了C_6和C_7异构化反应产物分布的特点,提出了烷烃在铂催化剂上异构化反应的类三元环新机理,它能很好地说明产物分布,特别是关于季碳异构体的生成。根据类三元环机理,烃分子首先在间位碳原子上各脱掉一个H原子,形成同铂原子以a,γ相连的三次甲基吸附态,它近似于铂环丁烷,异构化反应是由于铂环丁烷重排。可以按铂环丁烷的取代基位置与稳定性的关系对各种三次甲基吸附态的生成难易作比较,推测异构产物分布。实验结果与预测结果相符合。为了说明类三元环机理的理论合理性,对三次甲基吸附态的轨道相互作用和重排反应的对称性进行了初步讨论。
The characteristics of the distribution of C_6 and C_7 isomerization products were studied by using microreaction-chromatography (steady-state flow and pulsed techniques). A novel quasi-tricyclic ring mechanism for the isomerization of alkanes onto platinum catalysts was proposed, The product distribution is well illustrated, especially with respect to the formation of quaternary carbon isomers. According to the quasi-three-membered ring mechanism, the hydrocarbon molecules take off one H atom each at the meta carbon atom first to form the three methyl adsorption state which is connected with a and γ by the platinum atom. It is similar to platinum cyclobutane and isomerization The reaction is due to platinum cyclobutane rearrangement. According to the relationship between the substituent position and stability of platinum cyclobutane, we can compare the difficulty of the formation of various tertiary adsorption states and infer the distribution of isomeric products. The experimental results are consistent with the predicted results. In order to illustrate the theoretical rationality of the ternary-ring mechanism, the symmetry of the orbit interactions and the rearrangement reactions of the trimethylenes were discussed.