二重态下反应HCCO(~2A″)+O_2(~3∑_g^-)的势能面理论研究

Theoretical Study on the Doublet-State Potential Energy Surface of the Reactions between HCCO(~2A″) and O_2( ~3∑_g^-)

选用cc pVDZ ,cc pVTZ基组用密度泛函方法 (B3LYP)研究了基态羰游基自由基HCCO( 2 A″)与基态氧分子O2 ( 3 ∑ -g)反应的机理 ,在B3LYP/cc pVDZ优化的几何构型基础上 ,使用CCSD(T) /cc pVDZ方法进行了单点能校正 .此外 ,还采用基于B3LYP/6 3 1G 几何构型及振动频率的G3B3理论对所有驻点进行了更精确的能量计算 .结果表明 ,只需越过 6 3 1kJ/mol或6 2 3kJ/mol的位垒 ,氧分子中的一个氧原子便很容易地与羰游基中紧邻氢原子的碳原子相结合得到两个总能较比反应物低 88 11kJ/mol或 84 85kJ/mol的开环中间体 ,此二开环中间体很容易发生C—C—O—O环合或C—O—O环合从而转化为更稳定的环式异构体 (总能较比反应物低 14 9 81kJ/mol和 5 4 97kJ/mol) ,转化位垒分别为 8 73kJ/mol和 86 44kJ/mol.该二环式异构体均很容易分解为反应的最终产物H +CO +CO2 .其它可能的通道也在本文中有所探讨 .

Density functional (B3LYP) calculations, using the cc-pVDZ and cc-pVTZ basis sets, have been employed to study the reaction pathway involving ketyl radical (HCCO: 2A″) and oxygen molecule (O 2: 3∑ - g). Based on B3LYP/cc-pVDZ geometries, single point CCSD(T)/cc-pVDZ energy calculations have been performed to get more accurate energies. In addition, G3B3 theory with B3LYP/6-31G * geometries and frequencies has also been used for comparison. The obtained results show that the energy barriers are only 6.31 kJ/mol or 6.23 kJ/mol for the process of oxygen atom in O 2 attacking the terminal carbon of ketyl radical to form two open-ring intermediates, the total energies of which are 88.11 kJ/mol and 84.85 kJ/mol below the reactants, respectively. After that they could easily be converted to other two more stable annular isomers, the total energies of which are 149.81 kJ/mol and 54.97 kJ/mol below the reactants by cyclizing C—C—O—O or C—O—O with a barrier of 8.73 kJ/mol and 86.44 kJ/mol, respectively. Both of the annular isomers can easily be decomposed into the final products H+CO+CO 2. All other possible reaction channels are also reported.