武汉大学：《物理化学 Physical Chemistry》课程教学资源（PPT课件讲稿）11 Theories of elementary reaction

In this class 对化学反应的几个解释: 碰撞理论SCT 过渡态理论TST The last class 对反应模型的处理 复杂反应过程:平行,串级,连续, 稳态近似

对化学反应的几个解释: 碰撞理论 SCT 过渡态理论 TST 对反应模型的处理: 复杂反应过程: 平行, 串级, 连续, … 稳态近似 In this class, The last class

Theories of elementary reaction Simple collision theory (sct) for bimolecular reactions Transition state theory (tst) for bimolecular reactions

Theories of elementary reaction Simple Collision theory (SCT) for bimolecular reactions Transition state theory (TST) for bimolecular reactions

Two important empirical rule Rate equation (rule of mass action Arrhenius equation k=Expl RT

Two important empirical rule: Rate equation (rule of mass action) Arrhenius equation       = − RT E k A a exp

Type of Unimolecular Bimolecular Termolecular reaction reaction reaction reaction A 1013 101l 10 mol-l dms-1 mol-2 s-1 a seems related to collision frequency. exp Boltzmann distribution term RT

Type of reaction Unimolecular reaction Bimolecular reaction Termolecular reaction A 1013 s 1011 mol-1 dm3 s -1 109 mol-2 dm6 s -1 A seems related to collision frequency.       − RT Ea exp Boltzmann distribution term

Basic idea It is obvious that a molecule of a cannot react with a molecule of b unless the two reactant molecules can somehow interact This interaction can only take place if they come within a certain distance of each other. i.e. collides with each other 相互作用◆碰撞(不一定接触)

It is obvious that a molecule of A cannot react with a molecule of B unless the two reactant molecules can somehow interact. This interaction can only take place if they come within a certain distance of each other, i.e., collides with each other. Basic Idea: 相互作用 碰撞(不一定接触)

During 1920S, M. Trautz, W. Lewis, C. Hinshelwood et al. finally established a theory based on the collision which is called the simple collision theory. A reaction can take place only if the molecules of the reactants collide. Therefore, the rate constant of the reaction may be predicted by calculation of the collision frequency of the reactants

During 1920s, M. Trautz, W. Lewis, C. Hinshelwood et al. finally established a theory based on the collision, which is called the simple collision theory. A reaction can take place only if the molecules of the reactants collide. Therefore, the rate constant of the reaction may be predicted by calculation of the collision frequency of the reactants

The fundament of sct The premise of reaction is the collision between reactants The reaction rate of reaction is proportional to the collision frequency (么); Not all the collision is effective. The collision can be either non-reactive (elastic) collision or reactive couision Only the molecules posses energy excess to a critical value(e can lead to reactive collision

The fundament of SCT  The premise of reaction is the collision between reactants. The reaction rate of reaction is proportional to the collision frequency (Z);  Not all the collision is effective. The collision can be either non-reactive (elastic) collision or reactive collision. Only the molecules posses energy excess to a critical value (Ec ) can lead to reactive collision

The reaction rate of reaction is proportional to the collision frequency(z; AB kinetic theory of gases

The reaction rate of reaction is proportional to the collision frequency (Z); r = ZABq kinetic theory of gases

sct assumes that the molecules can be taken as rigid ball without inner structure. B d. and d are the diameter of a and b molecule respectively

SCT assumes that the molecules can be taken as rigid ball without inner structure. dA dB dA and dB are the diameter of A and B molecule, respectively

B不动

B不动