中文摘要：

利用密度泛函理论（DFT）方法计算了18种β—O—4连接的木质素模型化合物的Cβ—O键均裂解离能,讨论了模型化合物上不同位置羟基和甲氧基对解离能的影响,探究了取代基之间的交互作用。结果表明,Cα位羟基对解离能影响小。在R3位无甲氧基时,增加的Cγ位羟基对解离能影响较小;然而在R3位有甲氧基时,增加的Cγ位羟基氢与甲氧基氧之间形成氢键,显著增加醚键解离能。R3和R4位甲氧基均降低解离能,在Cγ位无羟基时,R3位甲氧基对解离能的降低作用最为显著;在Cγ位有羟基时,受Cγ位羟基与R3位甲氧基形成的氢键对醚键的稳定作用影响,R3位甲氧基对解离能的降低作用被弱化。R4位甲氧基不受Cγ位羟基的影响,对解离能的降低程度稳定。R1、R2位甲氧基对解离能影响较小也无特定规律,并且不与其他位置取代基产生交互作用。

英文摘要：

The substituted groups in lignin can influence the pyrolysis characteristics. Density functional theory （DFT） was employed to calculate the bond dissociation energies （BDEs） of the Cβ-O bonds in 18 lignin model compounds with Cβ-O-4 linkages. The model compounds were grouped and compared to discuss the effects of hydroxyl and methoxyl groups at different positions on the BDEs. The interactions between different groups were also studied, The results indicated that there was minor influence of the hydroxyl group at Ca. The hydroxyl group at C hardly affected the BDE when there was no methoxyl group at R3. However, when there was methoxyl group at R3, hydrogen bond would be formed between the hydroxyl group at Cγ and the methoxyl group at R2, and thus the spatial structure of the model compound would be strengthened and the BDE was increased. The methoxyl groups at R3 and R4 can reduce the BDEs. The methoxyl group at R3 can obviously reduce the BDEs when there was no hydroxyl group at Cγ. However, the reducing effect was weakened when there was hydroxyl group at Cγ, because the hydrogen bond between the methoxyl group at R3 and hydroxyl group at C would strengthen the ether bond. The methoxyl group at R4 was not influenced by the hydroxyl group at C, and thus the reducing effect on the BDE was stable. The methoxyl group at R1 and R2 had minor effects on the BDE, and moreover, it did not participate in the interactions with other functional groups.