CX2＋CH2O(X=F，Cl，Br)环加成反应的密度泛函理论计算

DFT calculations on the cycloaddition reaction of CX_2+CH_2O(X=F,Cl,Br)

用密度泛函理论，在B3LYP／6-311＋G（d）水平上研究了CX2＋CH2O（X=F，Cl，Br）环加成反应一条三过渡态三中间体路径的反应机理，全参数优化了反应势能面各驻点的几何构型，用内禀反应坐标（IRC）和频率分析方法，对过渡态进行了验证．用高级电子相关校正的耦合簇[CCSD（T）／6-311＋G（d）]方法对优化构型进行了单点能计算、采用经Wigner校正的Eyring过渡态理论和热力学方法，研究了该反应通道的热力学及动力学性质．从热力学和动力角度综合分析，该途径CF2与CH2O的环加成反应难以发生，而CCl2及CBr2与CH2O反应的适宜温度范围均为400-1000K，如此，反应既具有较大的白发趋势和平衡常数，又具有较快的反应速率.

The reaction mechanisms of CX2 ＋ CH2O （X= F, Cl, Br） have been studied theoretically by using the density functional theory （DFT） at the B3LYP/6-311 ＋ G（d） level. The single point energies along the minimum energy path have been further refined at CCSD（T）/6-311 ＋ G（d） level. The results show that the mechanisms for the title reactions all involve three transition states and three intermediates. The statistical thermodynamics and Eyring transition state theory with Wigner correction are used to study the thermodynamic and kinetic characters of this reaction from 100 K to 2050 K. The results show that the appropriate reaction temperature range are 400 to 1000 K for CCl2 and CBr2 at 1.0 Atm, in which the reaction has a bigger spontaneity capability, equilibrium constant （K） and higher rate constant （k）.