物理化学学报 >> 2004, Vol. 20 >> Issue (04): 400-404.doi: 10.3866/PKU.WHXB20040414

研究论文 上一篇    下一篇

Br2+2HI=2HBr+I2应机理的密度泛函理论

翟志才;柏云杉;王遵尧;王连生   

  1. 南京大学环境学院,南京 210093;盐城工学院化工系,盐城 224003
  • 收稿日期:2003-10-27 修回日期:2003-12-16 发布日期:2004-04-15
  • 通讯作者: 王遵尧 E-mail:wangzun315cn@sina.com

The Reaction Mechanism of Br2+2HI=2HBr+I2 by Density Functional Theory

Zhai Zhi-Cai;Bai Yun-Shan;Wang Zun-Yao;Wang Lian-Sheng   

  1. School of the Environment, Nanjing University, Nanjing 210093;Department of Chemical Engineering, Yancheng Institute of Technology, Yancheng 224003
  • Received:2003-10-27 Revised:2003-12-16 Published:2004-04-15
  • Contact: Wang Zun-Yao E-mail:wangzun315cn@sina.com

摘要: 用密度泛函理论(DFT)B3LYP方法,取3-21G**基组研究了气相反应Br2+2HI=2HBr+I2的机理,求得一系列四中心和三中心的过渡态.双分子基元反应Br2+HI→HBr+IBr和IBr+HI→I2+HBr的活化能(81.02和121.08 kJ•mol-1)小于Br2、HI和IBr的解离能(249.21、320.16和232.42 kJ•mol-1),故从理论上证明了标题反应将优先以分子与分子作用形式分两步完成.同时发现I原子与Br2分子反应生成较稳定的IBr2是一个无能垒过程,IBr2分解为IBr和Br原子的能垒为70.88 kJ•mol-1.

关键词: 溴, 碘化氢, DFT方法, 反应机理, 双分子反应

Abstract: The mechanism of reaction Br2+2HI=2HBr+I2 has been carefully investigated with density functional theory(DFT) at B3LYP/3-21G** level, and a series of four-centred and three-centred transition states have been obtained. The activation energies of the bimolecular elementary reactions Br2+HI→HBr+IBr and IBr+HI→I2+HBr(81.02 and 121.08 kJ•mol-1, respectively) are less than the dissociation energy of Br2, HI and IBr(249.21, 320.16, and 232.42 kJ•mol-1). It is thus theoretically proved that the title reaction occurs more easily in the bimolecular form with two medium steps. And it was also found that the reaction of I atom and Br2 to form stable IBr2 molecule is a process without energy barrier, and the energy barrier for decomposition of IBr2 into IBr and Br atom is 70.88 kJ•mol-1.

Key words: Bromine, Hydrogen iodide, Density functional theory(DFT) method,  Reaction mechanism, Bimolicular reaction