Dynamics and Kinetics Study of 鈥淚n-Water鈥?Chemical Reactions by Enhanced Sampling of Reactive Trajectories

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• 作者：Jun Zhang ; Y. Isaac Yang ; Lijiang Yang ; Yi Qin Gao
• 刊名：Journal of Physical Chemistry B
• 出版年：2015
• 出版时间：November 12, 2015
• 年：2015
• 卷：119
• 期：45
• 页码：14505-14514
• 全文大小：543K
• ISSN：1520-5207

文摘

High potential energy barriers and engagement of solvent coordinates set challenges for in silico studies of chemical reactions, and one is quite commonly limited to study reactions along predefined reaction coordinate(s). A systematic protocol, QM/MM MD simulations using enhanced sampling of reactive trajectories (ESoRT), is established to quantitatively study chemical transitions in complex systems. A number of trajectories for Claisen rearrangement in water and toluene were collected and analyzed, respectively. Evidence was found that the bond making and breaking during this reaction are concerted processes in solutions, preferentially through a chairlike configuration. Water plays an important dynamic role that helps stabilize the transition sate, and the dipole鈥揹ipole interaction between water and the solute also lowers the transition barrier. The calculated rate coefficient is consistent with the experimental measurement. Compared with water, the reaction pathway in toluene is 鈥渘arrower鈥?and the reaction rate is slower by almost three orders of magnitude due to the absence of proper interactions to stabilize the transition state. This study suggests that the 鈥渋n-water鈥?nature of the Claisen rearrangement in aqueous solution influences its thermodynamics, kinetics, as well as dynamics.