氯酸钾热分解反应机理的量子化学研究

A theoretical study of the thermal decomposition mechanism of potassium chlorate

采用Gaussian03量子化学程序包中考虑了电子相关性的密度泛函理论(DFT)的B3LYP方法,在6-311+G(3df)水平上对氯酸钾热分解反应路径进行了设计,对反应过程中可能存在的反应物、中间物、过渡态和产物的几何构型进行能量梯度全优化,同时计算得到了热分解反应的标准热力学量变。研究结果表明:由于氯酸根中存在的孤对电子以及(d-p)π配键的特殊属性,致使其稳定性较差。当氯酸钾吸热后,晶体扩散加快,振动振幅加大,致使部分氯酸根离子的Cl→O键断裂重新组合生成稳定的高氯酸根离子,当所有的氯酸钾都形成高氯酸钾时,高氯酸钾再发生分解反应放出氧气。这一热分解反应机理与前人的实验结果一致。

The mechanisms of the thermal decomposition reactions of potassium chlorate have been studied by using density functional theory （DFT） at the B3LYP/6-311 ＋ G（3df） level of the Gaussian 03 package. The geometries of all the species were optimized, and the thermochemical values and energies were calculated. We conclude that the special properties of the lone pair of electrons and （d-p）π coordinate covalent bond existing in potassium chlorate cause its structure to be very unstable. When potassium chlorate absorbs heat, the diffusion speed and the vibration amplitude of the crystal increase, which causes the C1→O bonds in CIO3^- to break and reconstruct, and the stable CIO4^- is subsequently formed. After all the potassium chlorate has been transformed into potassium perchlorate, the decomposition of potassium perchlorate occurs, with release of all the oxygen. These conclusions are in good agreement with the corresponding experimental data.