锗烯与甲醛环加成反应的理论研究

用从头算方法研究了单重态锗烯与甲醛环加成反应的机理,找到了反应的中间配合物和过渡态,并讨论了反应机理.在从头算的基础上,用统计热力学方法和过渡态理论计算了该反应在不同温度下的热力学函数的变化和动力学性质.结果表明,此反应由两步组成:(1)锗烯与甲醛反应生成了一中间配合物,是一无势垒的放热反应;(2)中间配合物异构化得到产物锗杂环氧甲烷,此步势垒经零点能校正后只有69.6kJ/mol(MP2/3-21G//3-21G).从热力学和动力学角度综合考虑,该反应在400～500K温度下进行为宜,此时,反应既有较大的自发趋势和平衡常数,又具有较快的反应速率.

Theoretical Study on the Cycloaddition Reaction of Germylene and Formaldehyde

The mechanism of singlet germylene and formaldehyde's cycloaddition reaction heve been studied by using ab initio method. We obtained the intermediate complex and transition state of this reaction, and then discussed the mechanism of the reaction. On the basis of ab initio and with the statistical thermodynamics method and transition-state theory we have calculated the reaction's change of thermodynamic functions and the quality of kinetic properties at different temperatures. The results show this reaction proceeds with two steps: (1) germylene and formaldehyde form an intermediate complex, which is a kind of exothermal reaction with no barrier; (2) the isomerized intermediate complex becomes the product, which after being corrected by zero-point energies, the barrier of reaction is 69.6 kJ/mol(MP2/3-21G//3-21G). On account for dynamics and thermodynamies, it is found that the reaction will not only have the larger sponlaneous tendency and equilibrum constants, but also the quicker reaction rate in the range of 400 K～500 K.