摘要
采用B3LYP、QCISD、MP2方法在6-311+G(d)基组水平上对叠氮酸与氨氰环加成反应进行了详细研究。首先对所有的反应物、过渡态和产物的构型进行了全参数优化,并用频率分析和内禀反应坐标(IRC)方法对过渡态进行确认。以步长为0.1(amu)1/2 bohr的内禀反应坐标方法在B3LYP/6-311+G(d)方法和基组水平上计算了内禀反应坐标s为(-3.00～3.00)(amu)1/2 bohr范围内反应的键长、振动频率、NBO电荷变化情况。根据统计热力学方法和用Wigner校正的Eyring过渡态理论,计算了(200～450)K温度范围内反应热力学函数及速率常数,探讨了温度对反应的影响。结果表明,反应经过过渡态TS生成5-AT的活化能为117.14 kJ/mol(B3LYP)、130.18 kJ/mol(QCISD)和106.24 kJ/mol(MP2),产物的相对能量为-74.24 kJ/mol(B3LYP)、-87.01 kJ/mol(QCISD)和-79.09 kJ/mol(MP2);反应随温度的升高更具有动力学优势,但在热力学上低温下更易于进行,因此,结合热力学和动力学因素,我们认为(300～350)K是该反应的适宜温度。
The cycloaddition reaction of hydrazoic acid and cyanamide were detailedly studied by B3LYP, QCISD and MP2 method with 6-311＋G^＋ level of theory. The geometries of all stationary points were optimized firstly. Vibrational analysis was carried out to confirm the transition state （TS） structures, and the intrinsic reaction coordinate （IRC） method was used to explore the minimum energy pathway （MEP）. The single-point energies of all stationary points were calculated by the same methods and level. The statistical thermodynamic method and Eyring transition state theory with Wigner correction were used to study the thermodynamic and kinetic characters within （200 - 450） K. The activation energy barriers for the reaction are 117.14 kJ.mol^-1 （B3LYP）, 130.18 kJ.mol^-1 （QCISD）, and 106.24 kJ-mol^-1 （MP2） respectively, and the relative energy of products are -74.24 kJ.mol^-1, -87.01 kJ.mo^-1, and -79.09 kJ.mol^-1 respectively. The reaction is favored with increase of temperature kinetically, but more easily taken place at low temperature thermodynamically, so we think that 300 to 350 K is most feasible temperature to the reaction.
出处
《计算机与应用化学》
CAS
CSCD
北大核心
2013年第6期595-599,共5页
Computers and Applied Chemistry
