利用理論計算探討CR2 (R = H, F, Cl, Br, CH3, NH2)與環氧乙烷(C2H4O)之反應機制研究

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Title:	利用理論計算探討CR2 (R = H, F, Cl, Br, CH3, NH2)與環氧乙烷(C2H4O)之反應機制研究 Computational Study of CR2 (R = H, F, Cl, Br, CH3, NH2) Radicals React with C2H4O
Authors:	李佳霓 Li, Chia-Ni
Contributors:	化學系應用化學碩士班
Keywords:	環氧乙烷取代基 CR2 Radicals React C2H4O
Date:	2015-06
Issue Date:	2015-08-05 13:58:09 (UTC+8)
Abstract:	環氧乙烷脫氧合成烯烴(乙烯)，在化學上是一個重要的有機合成方法。在近數十年來，已經有許多不同的反應物被應用在此方法上，環氧乙烷脫氧與carbene反應已經有被特別的研究。在我們的研究中，我們對CR2 (where R = H, F, Cl, Br, CH3, NH2) 與環氧乙烷的反應機制進行高層級的ab initio計算並探討其動力學反應速率。其中反應物、中間體、過渡態與產物都使用B3LYP/6-311++G(3df, 2p)的層級進行結構最佳化。從我們的位能曲面圖來看，所預測的H2C-OC2H4合成物(IM) 是經由過渡態(TS1) ，再進行脫氧過程，之後再經由TS2，最後形成產物乙烯和OCH2。我們也進行了不同取代基R = H, F, Cl, Br, CH3, NH2探討個別的活化能障與反應能量。此外，我們也使用CHAMRATE軟體，藉由過渡態理論與mRRKM理論計算了反應速率。總速率常數ktotal，在條件760 torr Ar氣壓力及298-3000 K溫度下計算出CF2的k值為k = 3.07×1022 T3.01exp(-11.19 kcal/mol-1/RT) 及C(CH3)2的k值為k = 4.86×1022T3.07exp(-20.62 kcal/mol-1/RT)。此外，在表格中我們針對個別的產物通道提供不同溫度與壓力條件下的反應速率常數k值。 The olefins were synthesis by deoxygenation of ethylene oxide is an important method. Various reagents have been employed for this purpose in the last several decades.In principle, the reaction pathways depended on the nature of the reagent and substrate. However, the deoxygenation of oxiranes with carbenes has been investigations widely.In our study,high level ab initio calculations have been performed to study the mechanisms and Kinetics of the CR2 (where R=H, F, Cl, Br, CH3, NH2) reacted with ethylene oxide. The reactant, intermediates, transition states, and products have been optimized at the B3LYP/6-311++G(3df,2p) level and their corresponding single-point energies also calculated with B3LYP/6-311++G(3df,2p) level. From the calculated potentail energy surface, we have predicted that H2C-OC2H4 complex (IM) formed via passing transition state (TS1), and the deoxygenation process occurs to form ethylene. The substituent group would be effect the reaction barrier and the rate-determing step (RDS). Futermore, we investigated the rate constant by transitionstate thoery and microcanonical Rice-Ramsperger-Kassel-Marcus RRKM with CHEMRATE program. The predicted total rate constant, ktotal, at the 760 torr Ar pressure can be represented by the equations: k=3.07×1022 T3.01exp(-11.19 kcal/mol-1/RT) and k=4.86×1022T3.07exp(-20.62 kcal/mol-1/RT) at T=298-3000Kfor CF2 and C(CH3)2, respectively. In addition, the rate constants for key individual product channels are provided in a table for different temperature and pressure conditions.
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