二甲苯异构化的反应化学

采用分子模拟计算方法计算了二甲苯的分子轨道、3种二甲苯与H+之间的相互作用,以及二甲苯异构化过程中2种分子内反应机理的能量路径和过渡态。结果表明,苯环骨架异构(简称1,3-迁移)的过渡态路径比甲基在苯环上转移(简称1,2-迁移)路径复杂,且1,3-迁移路径过渡态最高能垒值220.5kJ/mol远高于1,2-迁移的过渡态最高能垒85.1kJ/mol。由此推测,甲基在苯环上转移的1,2-迁移为二甲苯分子内异构化反应的主要机理路径。

Reaction Chemistry of Xylene Isomerization

By using molecular simulation technologies,the molecular orbitals of xylene,the interactions of H+ with xylene and the energy of each intermediate and transition state in xylene intramolecular isomerization(1,3-shift and 1,2-shift) were calculated and compared.The results showed that the mechanism of benzene ring transforming path(1,3-shift) was more difficult than the methyl shift path(1,2-shift).The highest transition state energy of 1,3-shift was 220.5 kJ/mol,which was higher than that of 1,2-shift(85.1 kJ/mol).It could be included that the 1,2-shift was the main mechanism for xylene intramolecular isomerization.