Impact of Water Molecules on the Isomerization of CH3S（OH）CH2 to CH3S（O）CH3： A Computational Investigation  

作　　者：Cao Jia Wenliang Wang Tianlei Zhang Loujun Gao Feng Fu Danjun Wang 

机构地区：[1]Key Laboratory for Macromolecular Science of Shaanxi Province, School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi' an, Shaanxi 710062, China [2]College of Chemistry & Chemical Engineering, Yan 'an University, Yan'an, Shaanxi 716000, China

出　　处：《Chinese Journal of Chemistry》2013年第10期1341-1347,共7页中国化学（英文版）

基　　金：Acknowledgement This work is supported by the National Natural Science Foundation of China （No. 21173139）, the foundation of Shannxi Education Department （No. 2013JK0667）, and the foundation of Yanan University （No. YDQ2013-16）.

摘　　要：The isomerization of CH3S（OH）CH2 to CH3S（O）CH3 in the absence and presence of water has been investigated at the G3XMP2//B3LYP/6-311 ＋ G（2df, p） level. The naked isomerization, the reaction without water, gives the high barrier height （21.56 kcal.mol^-1）. Three models are constructed to describe the water influence on the isomerization, that is, water molecules are the catalyst and the microsolvation, and water molecules act as the catalyst and microsolvation simultaneously. Our results show that the isomerization barrier heights of CH3S（OH）CH2 to CH3S（O）CH3 are reduced by 12.32, 11.04, and 7.80 kcal.mol^-1, respectively, when one, two, and three water molecules are performed as catalyst, in contrast to the naked isomerization. Moreover, the rate constants of the isomerization are calculated using the transition state theory with the Wigner tunneling correction over the temperature range of 240-425 K. We find that the rate constant of a single water molecule as the catalyst is 1.58 times larger than the naked isomerization at 325 K, whereas it is slower by 6 orders of magnitude when water molecule serves as the microsolvation at 325 K, compared to naked reaction. So the water-catalyzed isomerization of CH3S（OH）CH2 to CH3S（O）CH3 is predicted to be the key role in lowering the activation energy. The isomerization involving water molecules acting as mierosolvation is unfavorable under atmospheric conditions.The isomerization of CH3S（OH）CH2 to CH3S（O）CH3 in the absence and presence of water has been investigated at the G3XMP2//B3LYP/6-311 ＋ G（2df, p） level. The naked isomerization, the reaction without water, gives the high barrier height （21.56 kcal.mol^-1）. Three models are constructed to describe the water influence on the isomerization, that is, water molecules are the catalyst and the microsolvation, and water molecules act as the catalyst and microsolvation simultaneously. Our results show that the isomerization barrier heights of CH3S（OH）CH2 to CH3S（O）CH3 are reduced by 12.32, 11.04, and 7.80 kcal.mol^-1, respectively, when one, two, and three water molecules are performed as catalyst, in contrast to the naked isomerization. Moreover, the rate constants of the isomerization are calculated using the transition state theory with the Wigner tunneling correction over the temperature range of 240-425 K. We find that the rate constant of a single water molecule as the catalyst is 1.58 times larger than the naked isomerization at 325 K, whereas it is slower by 6 orders of magnitude when water molecule serves as the microsolvation at 325 K, compared to naked reaction. So the water-catalyzed isomerization of CH3S（OH）CH2 to CH3S（O）CH3 is predicted to be the key role in lowering the activation energy. The isomerization involving water molecules acting as mierosolvation is unfavorable under atmospheric conditions.

关 键 词：CH3S（O）CH3 CH3S（OH）CH2 water effect isomerization mechanism kinetic 

分 类 号：O561.3[理学—原子与分子物理] TE624.47[理学—物理]