摘要
应用密度泛函理论研究了CHOCHO与O2在单重态势能面上的反应机理.在M06/6-31G(d,p)水平上优化了各反应通道上各驻点(反应物、中间体、过渡态、产物)的几何构型,IRC计算证实了中间体和过渡态的真实性和相互连接关系,并计算了它们的振动频率和零点能,通过零点能校正计算了各反应通道的活化能.计算结果表明,乙二醛与氧气反应,存在生成乙醛酸和甲酸两条反应通道,两条通道的速控步骤的能垒分别为295.4kJ/mol和274.2kJ/mol,说明乙二醛分子很稳定,常温下很难被氧化成乙醛酸.相对而言,生成甲酸和CO2的通道为主反应通道.对各个反应通道分析可知,乙二醛生成乙醛酸的关键在于CHOCHO分子中的H原子转移至O2上的反应,由于有氧自由基的生成,氧化反应很难控制,生成的乙醛酸易被氧自由基继续氧化生成草酸.而在生成甲酸通道中,C-C键的断裂会造成甲酸和CO2的产生.
The unique molecular structure of the glyoxylic acid has brought itself into the wide use in the production and living.The reaction mechanism of CHOCHO interacting with the O2 on the singlet potential energy surface,and the geometries of all the stationary objects （the reactants,intermediates,transition states and products） were calculated using the density functional theory （DFT） at the M06/6-31G （d,p） level.The IRC analysis corroborates the authenticity of the intermediates and the transition states,as well as the correlation between them.By the vibration frequencies and the zero point vibration energies （ZPVE）,the activation energies of each reaction pathway was calculated.The results showed that two reaction channels were existed for the reaction,producing the glyoxylic acid and the methanoic acid,respectively.The energy barriers of the two paths＇ rate-determining steps were 295.4 kJ/mol and 274.2 kJ/mol,respectively.It suggested that the reaction of the CHOCHO oxidized into the glyoxylic acid was more difficult than that of the CHOCHO oxidized into the methanoic acid and the CO2 at room temperature,and the latter reaction is the main reaction path.Based on the analyzing each reaction channels,it is found that the reaction of the glyoxal oxidized into the glyoxylic acid determines to the hydrogen transfer from the glyoxal to the oxygen.Because of the appearance of the oxygen free radicals,the new generated glyoxylic acid is easier to be furtherly oxidized into the oxalic acid which is easily decomposed into the methanoic acid and CO2.
出处
《内蒙古师范大学学报（自然科学汉文版）》
CAS
北大核心
2013年第6期669-676,共8页
Journal of Inner Mongolia Normal University(Natural Science Edition)
基金
内蒙古自然科学基金资助项目(21063009)
内蒙古自然科学基金资助项目(2012MS0218)
内蒙古人才基金项目
关键词
乙二醛
乙醛酸
理论计算
反应机理
密度泛函理论
单重态势能面
glyoxal
glyoxylic acid
theoretical study
reaction mechanism
density functional theory （DFT）
singlet potential energy surface
