HNCO与XCH_2OH(X=CH_3、NH_2、OH、F)反应机理的理论研究  

Theoretical Study on the Mechanisms for the Reactions of HNCO with XCH_2OH(X=CH_3,NH_2,OH,F)

作　　者：石秋芝[1] 仝艳[1] 廖荣宝[1] 唐明生[1] 

机构地区：[1]郑州大学化学系,郑州450001

出　　处：《郑州大学学报（理学版）》2006年第2期101-106,共6页Journal of Zhengzhou University:Natural Science Edition

基　　金：国家自然科学基金资助项目;编号20272054

摘　　要：采用密度泛函(DFT)理论的B3LYP方法,在6-31++G(d,p)水平上按BERNY能量梯度解析全参数优化了HNCO和XCH2OH(X=CH3、NH2、OH、F)反应势能面上各驻点的几何构型,分别找到了这4个反应的过渡态,并通过振动频率分析确认了过渡态结构,通过内禀反应坐标(IRC)计算确认了最低能量反应途径(MEP).讨论了过渡态时的虚频振动模式,对各驻点进行了零点能(ZPE)校正,并计算了4个反应的活化能.研究结果表明,异氰酸的醇解反应是1个亲核加成反应,甲醇取代物和异氰酸分别是电子给体和电子受体,并且甲醇取代物的羟基氢在反应中发挥了重要作用;4个反应均为放热反应,反应中1个σ键和1个π键断裂,2个新的σ键生成;过渡态是四元环结构,由于CH3CH2OH、NH2CH2OH、OHCH2OH、FCH2OH分子中C、N、O、F原子电负性不同,四元环构型存在较明显的差异.The reaction mechanisms of HNCO with XCH2 OH （X = CH3, NH2 , OH, F） are investigated using density functional theory（DFT） at the B3LYP/6-31＋＋G（d,p） level. The transition states of the four reactions are found respectively and verified by frequency analysis. The minimum energy paths（MEP） are affirmed by intrinsic reaction coordinate （IRC） calculation and the imaginary vibration modes are discussed. The energy barriers of these reactions excluding the zero point energy are also calculated. The results show that alcoholysis reaction of isocyanic acid is a nucleophilic addition reaction with XCH2OH（X=CH3 ,NH2 ,OH,F） as an electronic donor and isocyanic acid as an acceptor,and that the hydroxyl hydrogen of XCH2 OH plays an important role in the reaction. All the four reactions are exothermal. During the course of each reaction,one σ bond and one π bond are broken ,and at the same time,two new σ bonds are formed. The shapes of the transition states and the four-ring structures are obviously different because of the differences of the electron-withdrawing ability of the atoms of C, N, O, F in the CH3CH2OH, NH2CH2OH, OHCH2OH and FCH2OH.

关 键 词：异氰酸 过渡态 内禀反应坐标 

分 类 号：O641[理学—物理化学]