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在密度泛函B3LYP/6-311G++**理论水平上,对气相和水相鸟嘌呤的两种形式(烯醇式与酮式)之间的质子转移(Path A:分子内和Path B:水助质子转移)互变异构体及其过渡态进行了几何构型全自由度优化,获得它们在气相和水相中的几何结构和电子结构,将PCM(极化连续介质模型)反应场溶剂模型用于水相计算.结果显示,在气相和水相中,烯醇式的稳定性大于酮式.Path A的过渡态结构为平面四元环,而Path B的过渡态结构为平面六元环;Path B所需活化能较低,约为Path A所需活化能的1/2.
Proton transfer between the two forms of the guanine (enol form and keto form) in the gas and aqueous phases (Path A: intramolecular and Path B: water at the B3LYP / 6-311G ++ ** density theory level Assisted proton transfer) tautomers and their transition states were optimized for their full freedom degrees of geometry, their geometries and electronic structures in the gas phase and the aqueous phase were obtained. The PCM (Polarization Continuous Media Model) reaction field solvent The model was used to calculate the water phase.The results showed that in the gas phase and the aqueous phase, the enol stability was greater than that of the ketones.Path A transition state structure was planar four-membered ring, while the transition state structure of Path B was plane six yuan Loop B requires less activation energy and is about 1/2 of the activation energy required by Path A.