叔丁氧基自由基引发氢迁移过程的理论研究

采用多种密度泛函理论方法(如CAM-B3LYP, M062x和wB97x方法), 并辅以极化连续介质模型对叔丁氧基自由基(^tBuO·)与一系列胺类、 烷烃、 醇类和醚类反应物之间氢迁移反应的反应机理进行研究. 计算结果表明, 这类氢迁移反应主要受熵的控制. 通过对液相平动熵和气相平动熵得到的活化自由能数据进行对比, 可以看出, 使用气相平动熵得出的活化自由能明显偏高于实验测量值, 而以液相平动熵计算的反应活化自由能垒与实际结果相近, 3种方法对胺类和烷烃类反应物体系得出的结果更可靠, 对醇类和醚类反应物体系自由能垒则略低.

Density Functional Theory Studies on the t-Butoxyl Radical Mediated Hydrogen Atom Transfer Reactions†

The reaction mechanisms of hydrogen abstractions from carbon by the t-butoxyl radical were investigated with several density functional theory(DFT) methods, such as CAM-B3LYP, M062x and wB97x. The results show that most of these reactions are dominated more by entropic than by enthalpic factor. The activation free energy barriers were calculated with both gas-phase translational entropy and solution translational entropy, in which those from ideal gas-phase translational entropy(output of Gaussian job) were much higher than the experimental estimations. It has been verified that free-energy barriers of amines and hydrocarbons reactions generated from solution translational entropies are close to the experimental measurements, but all these methods predict a little low free-energy barriers for alcohols and ethers reactions.