Cucinotta Clotilde S, Ruini Alice, Catellani Alessandra, Stirling András
CNR-INFM National Center on nanoStructures and bioSystems at Surfaces (S3), Italy.
Chemphyschem. 2006 Jun 12;7(6):1229-34. doi: 10.1002/cphc.200600007.
We have studied the keto-enol interconversion of acetone to understand the mechanism of tautomerism relevant to numerous organic and biochemical processes. Applying the ab initio metadynamics method, we simulated the keto-enol isomerism both in the gas phase and in the presence of water. For the gas-phase intramolecular mechanism we show that no other hydrogen-transfer reactions can compete with the simple keto-enol tautomerism. We obtain an intermolecular mechanism and remarkable participation of water when acetone is solvated by neutral water. The simulations reveal that C deprotonation is the kinetic bottleneck of the keto-enol transformation, in agreement with experimental observations. The most interesting finding is the formation of short H-bonded chains of water molecules that provide the route for proton transfer from the carbon to the oxygen atom of acetone. The mechanistic picture that emerged from the present study involves proton migration and emphasizes the importance of active solvent participation in tautomeric interconversion.
我们研究了丙酮的酮-烯醇互变异构，以了解与众多有机和生物化学过程相关的互变异构机理。应用从头算元动力学方法，我们模拟了气相和有水存在时的酮-烯醇异构化。对于气相分子内机理，我们表明没有其他氢转移反应能与简单的酮-烯醇互变异构竞争。当丙酮被中性水溶剂化时，我们得到了一种分子间机理以及水的显著参与。模拟结果表明，C去质子化是酮-烯醇转化的动力学瓶颈，这与实验观察结果一致。最有趣的发现是形成了短的水分子氢键链，这些链为质子从丙酮的碳原子转移到氧原子提供了途径。本研究得出的机理图景涉及质子迁移，并强调了活性溶剂参与互变异构转化的重要性。
