• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Secondary kinetic isotope effect on the photoenolization of triplet O-methylanthrones. A microcanonical transition state theory calculation
【24h】

Secondary kinetic isotope effect on the photoenolization of triplet O-methylanthrones. A microcanonical transition state theory calculation

机译：二级动力学同位素效应对三重态O-甲基蒽酮的光烯化作用微规范过渡态理论计算

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The energy profile for the tautomerization reaction of 1,4-dimethylanthrone in the first triplet electronic state obtained through electronic calculations (B3LYP/ 6-31G(d)) is used to calculate the rate constants for the process at a wide range of energies using a modified RRKM microcanonical statistical formalism that takes into account tunneling. Through partial or total substitution of the hydrogen atoms of the methyl groups by deuterium atoms, it is possible to evaluate different primary and secondary kinetic isotope effects (KIE). These results can be compared with experimental data for these processes taking place in solid matrix at extremely low temperatures (4-50 K). Such a comparison allows us to conclude that the reaction is taking place at energies just slightly below (around 0.5 kcal/mol) the adiabatic potential energy barrier, a result that was previously found for other related molecules so that this mechanism may be extended to the photoenolization of other o-aryl methyl ketones. Analysis of the different factors contributing to the primary and secondary KIEs discloses that at energies not far below the adiabatic barrier, the tunneling effect is not the only factor that accounts for the large KIE but the differences in the energy level distribution upon isotopic substitution may be the predominant factor at a certain range of negative energies (this is especially so for the case of primary KIE). At positive energies (above the barrier) the levels factor is always the dominant factor in the total KIE.
机译：通过电子计算（B3LYP / 6-31G（d））获得的第一三重态电子态的1,4-二甲基蒽的互变异构化反应的能谱用于计算该方法在宽范围的能量下的速率常数修正的RRKM微规范统计形式，其中考虑了隧道效应。通过用氘原子部分或完全取代甲基的氢原子，可以评估不同的一级和二级动力学同位素效应（KIE）。这些结果可以与在极低温度（4-50 K）下在固体基质中进行的这些过程的实验数据进行比较。这样的比较使我们可以得出结论，该反应是在刚好低于绝热势能垒（约0.5 kcal / mol）的能量下发生的，该结果先前是在其他相关分子中发现的，因此该机理可以扩展到其他邻芳基甲基酮的光烯化。对影响主要和次要KIE的不同因素的分析表明，在绝热壁垒不远处的能量下，隧穿效应不是导致大KIE的唯一因素，但是同位素取代时能级分布的差异可能是在一定范围内的负能量是主要因素（对于主KIE尤其如此）。在正能量下（在势垒以上），电平因子始终是总KIE中的主导因子。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号