H_2O+Cl→HCl+OH反应中D同位素的动力学效应的理论研究

The Theoretical Studies of Deuterium Kinetic Isotope Effect(KIE) on H 2O+Cl→HCl+OH

根据传统过渡态、变分过渡态理论计算了Ｈ２Ｏ＋Ｃｌ→ＨＣｌ＋ＯＨ（Ｒ１）反应中Ｄ代替Ｈ后的同位素动力学效应（ＫＩＥ），得到了ＨＯＤ＋Ｃｌ→ＤＣｌ＋ＯＨ（Ｒ２）、ＤＯＨ＋Ｃｌ→ＨＣｌ＋ＯＤ（Ｒ３）反应不同的ＫＩＥ值。对ＫＩＥ进行了分解，讨论了平动（ｔｒａｎｓ）、转动（ｒｏｔ）、振动（ｖｉｂ）等各种因素的作用。在反应Ｒ２中，由于ＨＯＤ中ＯＤ键直接参与反应，Ｄ同位素的ＫＩＥ很大，对Ｒ２的ＫＩＥ分解表明，振动对ＫＩＥ的贡献最大。在反应Ｒ３中，由于ＨＯＤ中ＯＤ键并不直接参与反应，Ｄ同位素的ＫＩＥ较小。

Conventional transition state theory,varational transition state theory calculations have been carried out for the case of the deuterium kinetic isotope effect(KIE)in the reactions HOD+Cl→DCl+OH(R2)and HOD+Cl→HCl+OD(R3) Factorization analyses of the KIE are presented to illustrate the contributions of translation,rotation,and vibration Because the OD bond in R3 reaction is a spectator,the DKIE in the R3 is less than the D KIE in the R2.It is concluded that vibrational contribution is the dominant in the R2 reaction.