物理化学学报
物理化學學報
물이화학학보
ACTA PHYSICO-CHIMICA SINICA
2014年
8期
1456-1464
,共9页
Au(111)面%肉桂醛%密度泛函理论%苯丙醛%选择性加氢机理
Au(111)麵%肉桂醛%密度汎函理論%苯丙醛%選擇性加氫機理
Au(111)면%육계철%밀도범함이론%분병철%선택성가경궤리
Au(111) surface%Cinnamaldehyde%Density functional theory%Hydrocinnamaldehyde%Selective hydrogenation mechanism
采用密度泛函理论并结合周期性平板模型的方法,优化了肉桂醛在Au(111)面上的吸附模型,并详细探讨了肉桂醛在Au(111)面上选择性加氢的反应机理(C＝O, C＝C以及1,4共轭加成机理).计算结果表明,肉桂醛以C＝O和C＝C协同吸附于Au(111)面上时,吸附构型最稳定.此时,不同吸附模式的吸附能平均在140.0 kJ?mol-1.通过搜索不同机理下每个基元反应的过渡态,得出肉桂醛在Au(111)面上最可能的选择性加氢产物为苯丙醛,且其按照1,4共轭加成机理间接得到苯丙醛比C＝C直接加氢机理具有更低的活化能.具体反应过程为：肉桂醛C＝O的O优先加H形成烯丙基型中间体,继而该中间体中与苯环相连的C原子继续加H形成烯醇(ENOL),最终烯醇异构成苯丙醛.其中ENOL的生成过程所需的活化能最高,是反应的控速步骤.
採用密度汎函理論併結閤週期性平闆模型的方法,優化瞭肉桂醛在Au(111)麵上的吸附模型,併詳細探討瞭肉桂醛在Au(111)麵上選擇性加氫的反應機理(C＝O, C＝C以及1,4共軛加成機理).計算結果錶明,肉桂醛以C＝O和C＝C協同吸附于Au(111)麵上時,吸附構型最穩定.此時,不同吸附模式的吸附能平均在140.0 kJ?mol-1.通過搜索不同機理下每箇基元反應的過渡態,得齣肉桂醛在Au(111)麵上最可能的選擇性加氫產物為苯丙醛,且其按照1,4共軛加成機理間接得到苯丙醛比C＝C直接加氫機理具有更低的活化能.具體反應過程為：肉桂醛C＝O的O優先加H形成烯丙基型中間體,繼而該中間體中與苯環相連的C原子繼續加H形成烯醇(ENOL),最終烯醇異構成苯丙醛.其中ENOL的生成過程所需的活化能最高,是反應的控速步驟.
채용밀도범함이론병결합주기성평판모형적방법,우화료육계철재Au(111)면상적흡부모형,병상세탐토료육계철재Au(111)면상선택성가경적반응궤리(C＝O, C＝C이급1,4공액가성궤리).계산결과표명,육계철이C＝O화C＝C협동흡부우Au(111)면상시,흡부구형최은정.차시,불동흡부모식적흡부능평균재140.0 kJ?mol-1.통과수색불동궤리하매개기원반응적과도태,득출육계철재Au(111)면상최가능적선택성가경산물위분병철,차기안조1,4공액가성궤리간접득도분병철비C＝C직접가경궤리구유경저적활화능.구체반응과정위：육계철C＝O적O우선가H형성희병기형중간체,계이해중간체중여분배상련적C원자계속가H형성희순(ENOL),최종희순이구성분병철.기중ENOL적생성과정소수적활화능최고,시반응적공속보취.
The adsorption behavior and selective hydrogenation reaction mechanisms (C=O addition, C=C addition, and 1,4-conjugate addition) of cinnamaldehyde on an Au(111) surface were investigated by density functional theory combined with a periodic slab model. The adsorption energies of various adsorption models were obtained to determine the preferred adsorption configuration. The calculated results indicate that the most stable adsorption configuration involved the C=O and C=C double bond adsorbed on the Au(111) surface, with an average adsorption energy of 140.0 kJ?mol-1. The transition states of each elementary reaction for al possible reaction mechanisms were also located. Comparison of the activation energy barriers revealed hydrocinnamaldehyde (HCAL) to be the most likely selective hydrogenation product of cinnamaldehyde on an Au(111) surface. In addition, the 1,4-conjugate addition mechanism, which generates 3-phenyl-1-propen-1-ol (ENOL) that readily tautomerizes to HCAL, required less activation energy than did the C=C direct addition mechanism. The dominant reaction pathway involved an O atom of cinnamaldehyde preferential y hydrogenating to generate a more stable al yl intermediate. Another H atom then added to a C atom directly connected to the phenyl ring of the al yl intermediate to yield ENOL. Final y, ENOL tautomerized to HCAL. Throughout the process, the generation of ENOL is the rate-determining step, for which the highest activation energy barrier was required.
