中文摘要：

通过密度泛函理论计算研究了1,2-环己二酮（α-CHD）基态光解离反应的势能面.通过IRC方法确定了5个主要的反应通道,相应的产物分别为P1（c-C5H8O＋CO）,P2（2C2H4＋2CO）,P3（CH2CHCH2CH2CHO＋CO）,P4（2CH2CO＋C2H4）和P5（CH3CHCO＋CH2CHCHO）.获得了反应过程中反应物、产物、中间体和过渡态的结构参数.详细阐述了这些通道的反应过程,分析了其反应机理,总结出最优的反应路径为α-CHD→c-C5H8O＋CO.理论分析与实验结果相符.获得的结果为进一步进行与1,2-环己二酮相关的研究提供有价值的信息.

英文摘要：

The α-cyclohexanedione（α-CHD） molecule is an important structural unit in the six-membered ring systems with a large number of biologically meaningful molecules which have been found. It has important applications in synthetic science also. It is found that some fragments can be obtained through vacuum ultraviolet absorption spectrum and induction photolysis experiments for α-CHD molecules. In order to understand the dissociation reaction mechanism of α-CHD and reveal the resource of those fragments, the potential energy surface of the dissociation reaction for α-CHD molecules in ground state is studied by B3 LYP and CCSD（T） methods. The reaction paths of the products are obtained, such as P1（c-C5H8O ＋ CO）, P2（2 C2H4＋ 2 CO）, P3（CH2CHCH2CH2CHO ＋ CO）, P4（2C2H2O ＋ C2H4）,P5（CH3CHCO ＋ CH2CHCHO）. And the structure parameters of the reactant, products, intermediates and transition states in the reaction processes are also obtained. Their reaction mechanisms can be summarized as the isomerization and dissociation processes, and these processes mainly involve the hydrogen atom transfer, ring-opening and C—C bond cleavages. A reaction channel in which α-CHD dissociates into cyclopentanone and CO needs lower energy, so it is more advantage our to make dissociation study than other studies. In addition, we think that α-dissociation reaction cannot occur directly in ground state from our calculations. Based on the UV photolysis experiment of α-CHD with a wavelength of 253.7 nm（112.7 kcal/mol） and the theoretical calculation of potential energy surface in ground state, we obtain that Path 1（α-CHD→ c-C5H8O ＋ CO） is the most possible channel, Path 3（α-CHD→ CH2CHCH2CH2CHO＋ CO） is the next, and Path 5（α-CHD→ CH3 CHCO ＋ CH2CHCHO） is the third, while Path 2（α-CHD→2 C2H4＋ 2CO） and Path 4（α-CHD→2 CH2CO ＋ C2H4） are difficult to be achieved. Soc-C5H8O and CO are the major fragment products, CH2CHCH2CH2 CHO is the subsidiary one, maybe a mino