论化学反应动力学中的稳态假设  

On the Steady State Hypothesis in Chemical Kinetics

作　　者：钱人元[1] 

机构地区：[1]中国科学院化学研究所分子科学中心,北京100080

出　　处：《化学通报》2003年第11期723-729,共7页Chemistry

摘　　要：对单分子气相反应Lindemann机理提出了一个不用稳态假设的动力学新表述 ,并指出经典表述中的稳态假设是主观硬性加上的 ,缺少了一个条件。当反应气体压强变小时 ,经典表述中虽然应用稳态假设 ,但实际上是高活性中间产物的近似 ,并不真正存在稳态。稳态假设的适用性有两种不同的近似本质 ,一是平衡态近似或真稳态 ,另一是高活性中间产物近似 ,应予分辨。过去文献中往往把两者混在一起 ,这会导致得不到一般性结论 ,或所得一般性结论会有错误。文中也讨论了在复杂反应中真稳态的存在 ,而平衡态和真稳态的建立 ,都需经过一个初期瞬间过程 ,而高活性中间产物近似没有初期瞬间过程 ,因为不是一个形成稳态的过程。A new formulation of the Lindemann mechanism of unimolecular reactions in gaseous phase is presented, without the use of steady state hypothesis. It is pointed out that the steady state hypothesis used in the classical formulation is an ad hoc assumption, a condition is missing. In the regime of low reactant gas pressure, although steady state hypothesis is applied in the classical formulation, it is actually highly reactive intermediate approximation, a steady state actually does not exist. The applicability of steady state hypothesis has two distinctive nature of approximation, one is an equilibrium state, or a true steady state, approximation and the other is a highly reactive intermediate approximation. These two distinctive nature of approximation should be carefully distinguished. In the past literature these two cases of applicability of steady state hypothesis is quite often mixed_up, so that no general conclusion could be reached, or the general conclusion arrived at may be wrong. The only possible case of realizing a true steady state in a complex reaction is pointed out. In such a case the build up of an equilibrium state or a true steady state always goes through an initial transient stage, while a highly reactive intermediate approximation does not go through an initial transient stage, just because it is not a process to form a steady state.

关 键 词：化学反应动力学 稳态假设 单分子反应 Lindemann机理 

分 类 号：O643.1[理学—物理化学]