【摘 要】
：
采用MP2/6-31G(d,p)从头计算方法优化获得硝基胍两种异构体及过渡态的几何结构,在相同水平上计算了各驻点频率,并进行了IRC分析.利用过渡态理论,计算了在200～1773 K的H迁移异
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采用MP2/6-31G(d,p)从头计算方法优化获得硝基胍两种异构体及过渡态的几何结构,在相同水平上计算了各驻点频率,并进行了IRC分析.利用过渡态理论,计算了在200～1773 K的H迁移异构化反应的速率常数. 结果表明, β型硝基胍中形成大范围的离域大∏键,存在显著的共轭效应使其比α型稳定,能量比α型低28.16 kJ/mol;硝基胍由α型向β型H迁移异构化反应的活化能为132.95 kJ/mol. 298 K时速率常数为1.99×10-11 s-1,平衡常数为1.00×105;硝基胍的异构化是一个典型的同面H迁移放热反应,随温度升高,平衡常数逐渐减小,不利于α型通过H迁移向β型转化.
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