Abstract:

The selective hydrogenation reaction mechanisms (C=O addition mechanism, C=C addition mechanism, and 1,4-conjugate addition mechanism) of cinnamaldehyde over M₁₃(M=Au, Pt) were investigated using density functional theory. The transition states of each elementary reaction step in selective hydrogenation of cinnamaldehyde were explored by the complete LST/QST method on the basis of optimized stable adsorption configurations, hence the activation energy and reaction heat were obtained. The calculation results showed that on Au₁₃ cluster, cinnamaldehyde most likely follows 1,4-conjugate addition mechanism to produce very unstable ENOL, and tautomerizes to benzenepropanal(HCAL), of which the total hydrogenation process is almost exothermic. However, on Pt₁₃ cluster, it most likely follows the C=O addition mechanism to generate cinnamyl alcohol(COL) followed by further hydrogenation to saturated alcohols, of which the total hydrogenation process is almost endothermic.

Key words: cinnamaldehyde, M₁₃ cluster, density functional theory, hydrogenation

摘要：

采用密度泛函理论系统地研究了肉桂醛在正二十面体M₁₃(M=Au,Pt)团簇上的选择性加氢反应机理(C=O,C=C以及1,4共轭加成机理)。在稳定吸附构型的基础上,通过Complete LST/QST方法探索肉桂醛选择性加氢反应中各基元反应的过渡态,得到各反应的活化能和反应热。计算结果表明:肉桂醛在Au₁₃团簇最可能发生1,4共轭加成得到烯醇,但烯醇很不稳定,会发生异构生成苯丙醛,反应总体放出热量;肉桂醛在Pt₁₃团簇最可能发生C=O加成得到肉桂醇,肉桂醇进一步加氢得到饱和醇,反应总体吸收热量。

关键词: 肉桂醛, M₁₃团簇, 密度泛函理论, 加氢