理论研究单个水或甲酸分子对乙酰基异构化的影响  

Theoretical Study of the Effect of Single Molecule of Water or Formic Acid on the Isomerization of Acetyl Radical

作　　者：翟艳玲[1] 陈广慧[1] 陈伟[1] 

机构地区：[1]汕头大学理学院,汕头515063

出　　处：《青岛大学学报（自然科学版）》2015年第4期18-23,33,共7页Journal of Qingdao University(Natural Science Edition)

基　　金：广东省自然科学基金(批准号:s2013010014476)资助;汕头大学国家自然科学基金培育项目(批准号:NFC13001)资助

摘　　要：在M06-2X、B3LYP、MP2和MC-QCISD水平下,理论研究了大气中的单个水和甲酸分子催化乙酰基异构化的反应机理,发现产物均为CH2COH自由基。研究结果表明,裸反应的活化能为81.2kcal·mol-1,而加上水和甲酸分子活化能分别降低到46.2和29.0kcal·mol-1,表明它们均能与乙酰基通过氢键形成稳定的络合物,以便有效地催化异构化反应。在298K,1标准大气压条件下,通过直接动力学计算发现,裸反应的速率常数为6.49×10-47cm3·molecule-1·s-1,水和甲酸催化反应比其速率常数分别增加24和33个数量级。考虑大气中各物种浓度后,发现裸反应速率为4.96×10-29s-1,水或甲酸催化该反应的速率分别为2.55×107和9.52×109s-1,当大气中水分子或甲酸浓度较高时,乙酰基异构化反应生成CH2COH自由基可能性很大。The isomerization reaction of acetyl radical with single water or formic acid molecule was investigated at the MP2,M06-2X,B3 LYP,and MC-QCISD levels.It found that all the reaction products are CH2 COH radical.The calculated results shown that single water or formic acid molecule can effectively reduce the activation energy of the isomerization of the CH3 CO radical to CH2 COH.The barrier of the naked reaction is 81.2kcal·mol-1,but reduced to 46.2or 29.0kcal·mol^-1 with the catalyzation of water or formic acid,respectively.At 298 Kand 1bar,the rate constant of naked reaction is 6.49×10^-47 cm^3·molecule^-1·s^-1,while that catalyzed by water molecule is increased by 24 orders of magnitude,the largest enhancement in the rate,by over 34 orders of magnitude,is with formic acid.Considering the concentration of species in the atmosphere,the rate of naked reaction is 4.96×10^-29s^-1,while that catalyzed by water or formic acid,the rate is 2.55×107 and 9.52×10^9s^-1,respectively.Thus,the isomerization from CH3 CO to CH2 COH radical has great possibility to react at high concentration of water or formic acid in the atmosphere.

关 键 词：水分子催化 甲酸分子催化 乙酰基异构化 速率常数 

分 类 号：O641[理学—物理化学]