...
  • 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 >Kinetics and Thermochemistry for the Gas-Phase Keto-Enol Tautomerism of Phenol <-> 2,4-Cyclohexadienone
【24h】

Kinetics and Thermochemistry for the Gas-Phase Keto-Enol Tautomerism of Phenol <-> 2,4-Cyclohexadienone

机译：苯酚<-> 2,4-环己二烯酮气相酮-烯醇互变异构的动力学和热化学

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

Isomerization of phenol is considered an important step in the metabolism of aromatic compounds and it may be the first step of phenol decomposition in thermal reaction systems. Ideal gas thermochemical properties, ΔH°_(f,298), S°_(298), and C_p°(T) (300 ≤ T/K ≤ 1500) for two keto forms of phenol (1), 2,4-cyclohexadienone (2), and 2,5-cyclohexadienone (3), are calculated in this study. ΔH°_(f,298) (2) is computed as -4.4 ± 2.4 kcal/mol at CBS-QB3 level and isodesmic reactions are utilized to minimize the systematic calculation errors. ΔH°_(f,298) (3) = -6.0 ± 2.4 kcal/mol is obtained from the total energy difference between 2 and 3. The two keto tautomers are less stable than their enol form, phenol, ΔΔH°_(f,298) (1 <-> 2) = -18.6 and ΔΔH°_(f,298) (1 <-> 3) = -17.0 kcal/mol, respectively. The rate constant through transition state 4 for the tautomerization of phenol to 2,4-cyclohexadienone is obtained as 8.06 * 10~(12) exp(-69.4 kcal mol~(-1)/RT) s~(-1). The equilibrium constants are computed as 7.15 * 10~(-14) and 2.16 * 10~(-13) at 298 K for reactions 1 <-> 2 and 1 <-> 3, respectively. Kinetic parameters for the unimolecular isomerization and decomposition of 2 are also determined. IRC analysis on the transition state indicates that decomposition occurs by cleavage of the weak bond between allylic carbon and carbonyl carbon (73.1 kcal/mol, doubly allylic) to cis-1,3-butadienyl-4-ketene. ΔH_(rxn) of these paths are estimated. ΔH°_(f,298) of cis- and trans-1,3-butadienyl-4-ketenes are determined as 24.5 and 19.2 kcal/mol, respectively. ΔH°_(f,298) of species 2 and 3 are also calculated at the CBS-Q//B3LYP/6-31G(d,p) level and compared with the CBS-QB3 results.
机译：苯酚的异构化被认为是芳香族化合物代谢的重要步骤，它可能是热反应系统中苯酚分解的第一步。两种酮型苯酚（1），2,4-的理想气体热化学性质ΔH°_（f，298），S°_（298）和C_p°（T）（300≤T / K≤1500）这项研究计算了环己二酮（2）和2,5-环己二酮（3）。在CBS-QB3水平下，ΔH°_（f，298）（2）计算为-4.4±2.4 kcal / mol，并利用等渗反应将系统计算误差降至最低。 ΔH°_（f，298）（3）= -6.0±2.4 kcal / mol由2与3之间的总能量差获得。两种酮型互变异构体的稳定性低于其烯醇形式苯酚ΔΔH°_（f ，（298）（1 2）＝-18.6和ΔΔH°_（f，298）（1 3）＝-17.0kcal / mol。获得了用于苯酚互变异构为2,4-环己二酮的过渡态4的速率常数，为8.06 * 10〜（12）exp（-69.4 kcal mol〜（-1）/ RT）s〜（-1）。对于反应1 2和1 3，在298 K下的平衡常数分别计算为7.15 * 10〜（-14）和2.16 * 10〜（-13）。还确定了2的单分子异构化和分解的动力学参数。 IRC对过渡态的分析表明，分解是通过将烯丙基碳和羰基碳之间的弱键（73.1 kcal / mol，双烯丙基）裂解为顺1，3-丁二烯基-4-酮而发生的。估计这些路径的ΔH_（rxn）。顺式和反式1,3-丁二烯基-4-酮的ΔH°（f，298）分别确定为24.5和19.2 kcal / mol。还以CBS-Q // B3LYP / 6-31G（d，p）水平计算了物种2和3的ΔH°_（f，298），并将其与CBS-QB3结果进行了比较。

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