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用从头算自洽场分子轨道UHF方法,在3-21G基组上,研究了丙酮分子光解离为乙酰基(CH_3CO)和甲基(CH_3)的解离反应.计算是在(n,π＊)激发三重态势能面上.(n,π)激发三重态的丙酮分子途经一个C_1对称性的过渡态(T S1)生成一个(n,π＊)激发态的乙酰基和一个基态的甲基.该过程是断键和基团构象转化协同进行的单步反应.计算的垂直激发能和激发三重态位能面上的反应活化位垒分别为279.43和141.04kJ·mol~(-1).这些能量值与丙酮光解的实验条件相吻合.用相同的计算方法,进一步探讨了基态乙酰基分解为CH_3和CO分子的热解离反应.解离过程的过渡态(TS2)以σ键伸长为特征.该过程是一个断键在先,基团构象转化在后分开进行的单步反应.计算的活化位垒为56kJ·mol~(-1)与实验值(75kJ·mol~(-1))相接近.
The dissociation reaction of acetone molecule to acetyl group (CH_3CO) and methyl group (CH_3) was studied on the 3-21G basis set by using ab initio UHF method. The calculation is based on (n, π *) Excited Triplet Potential (n, π) The acetone molecule that triggers the triplet state generates an (n, π *) excited-state acetyl group and a ground state methyl group via a C 1 symmetric transition state (T S1) .This process is a one-step reaction that synergistically proceeds with the conformational transition of the radical and the radical.The calculated activation energies of the vertical activation energy and the activation energy barrier on the excited triplet energy surface are 279.43 and 141.04 kJ · mol -1, respectively The energy values agree well with the experimental conditions for the photolysis of acetone. The thermal dissociation of the ground state acetyl groups into CH_3 and CO molecules is further studied by the same calculation method. The transition state (TS2) The process is characterized by a single-step reaction in which the conformational transitions of the groups are separated afterwards, the calculated activation barrier is 56 kJ · mol -1 and the experimental value is 75 kJ · mol -1 )).