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Title: A theoretical study of hetero diels-alder reactions
Keywords: hetero,Diels-Alder,concerted,stepwise,polarized,diradical
Issue Date: 8-Aug-2003
Citation: LIU XIANGHUI (2003-08-08). A theoretical study of hetero diels-alder reactions. ScholarBank@NUS Repository.
Abstract: In this thesis, we studied the reaction mechanism and possible factors that would affect the concerted pathway for reactions between CH2=X(X= O, S, Se, NH, PH, AsH, CH2, SiH2a?|) and 1,3-butadiene. Reactions have a lower energy barrier when X is a second-row or third-row atom. The excitation energy between the singlet and triplet states is the most important factor that affects the energy barrier. We also studied the reaction of 2-aza-1,3-butadiene and ethylene. Comparisons show that it is similar to the reaction of 1,3-butadiene and ethylene. Lewis acid catalyst BF3 helps greatly to lower down the concerted pathway energy barrier but little for the stepwise pathway. Two methyl groups help greatly to lower the energy barrier of the stepwise pathway and decrease the difference of energy barrier between the concerted and the stepwise pathway to only 4.6 kcal/mol. The tertiary carbenium ion formed in the reaction plays an important role. We also studied the reaction between tetrafluoroethylene and 2-aza-1,3-butadiene. The energy barrier of the stepwise pathway is slightly higher than that of the concerted pathway by 0.3 kcal/mol. These provide two possible ways to find preferred stepwise pathways over the concerted pathway. Keywords: G2 and DFT Theory; hetero Diels-Alder reaction; 2-aza-1,3-butadiene; concerted and stepwise pathways; polarized stepwise pathway and diradical stepwise pathway; tetrafluoroethylene(TFE); 1,1-dimethyl-ethylene
Appears in Collections:Master's Theses (Open)

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