<i>Ab Initio</i> Molecular Dynamics Study of the Reduction of Acetone by the Hydrated Electron

We have investigated the reaction dynamics of the reduction of acetone by the solvated electron in water using ab initio molecular dynamics simulations at 298 and 373 K. The rate constants derived from the simulations are consistent with experimental observations that the reaction has a low activation energy. Detailed analyses carried out to shed light on the mechanism of the reaction show that solvent reorganization plays a key role as a reaction coordinate, as expected from the Marcus electron transfer theory. However, constrained density functional theory calculations indicate that the electronic coupling is large, placing the reaction in the adiabatic limit. Indeed, the activation energies and rate constants of the simulations are in accordance with the predictions of adiabatic Marcus theory.本研究采用从头算分子动力学（ab initio molecular dynamics）模拟方法，在298 K与373 K条件下，探究了水溶液中溶剂化电子（solvated electron）还原丙酮（acetone）的反应动力学过程。模拟得到的速率常数与实验观测结果一致，即该反应具有较低的活化能。为阐明该反应机理所开展的详细分析表明，正如马库斯电子转移理论（Marcus electron transfer theory）所预期的那样，溶剂重组作为反应坐标发挥了关键作用。然而，约束密度泛函理论（constrained density functional theory）计算结果显示，该反应的电子耦合强度较大，使其处于绝热极限（adiabatic limit）范畴。实际上，模拟得到的活化能与速率常数均符合绝热马库斯理论（adiabatic Marcus theory）的预测结果。