Payne Rearrangement Of The Reaction Mechanism

Epoxy compound is a - C - C - structure of ternary ring ether. Due to the existence of ring, epoxy compound has high reactivity, for acid and nuclear reagent are very sensitive,can open-loop with halogenating hydrogen, water, alcohol, amine, grignard reagent and many kinds of reagent, is the synthetic material ofβ-halohydrin, 1,2- glycol,β- hydramine, polyether and higher alcohols. It is the important intermediates of organic synthesis. It can be produced by catalytic oxidation of olefins or acid oxidation. It also can be produced byβ-halohydrin react with base. As the important intermediates of organic synthesis, the position of the epoxy ring usually can control the whole reaction mechanism. The epoxy migration can make the reaction route more flexible, product more changeable.Historically, the first documented report of a possible Payne rearrangement in carbohydrate chemistry was probably that ofBritish chemists, Lake and Peat. The most influential paper on this type of reaction, however, was Payne's 1962 publication describing the equilibration (epoxide migration) of racemic simple 2,3-epoxy alcohols under basic conditions.The Payne rearrangement reaction has been applied widely in the organic synthesis, and many investigations are to optimize the reaction conditions of composing alkenes. To the best of our knowledge, the mechanism of the Payne rearrangement reaction has not been studied by using quantum-chemical methods. So studying the mechanism of the reaction by using the method of quantum chemistry calculation is of great significance.Considering the above facets, we start our systemic study the mechanism of Payne rearrangement reaction, the influence of the substituents and solvent by using the B3LYP method in the density functional theory. The thesis consists of five parts as follows:1. A DFT study for the mechanism of Payne rearrangement reaction Density functional theory (DFT) has been used to study the mechanism of Payne rearrangement reaction at the B3LYP/6-311+G (d, p) levels. The transition states and the energy barriers of the reactions are obtained. The mechanism can be described by the following reaction sequences:When no hydroxyl catalytic:When a hydroxyl catalytic:When no hydroxyl catalytic, the reaction is an elementary reaction, has a higher activation energy, to realize the epoxy ring migration. When a hydroxyl catalytic, the first step and the third step are typical ion reaction, react very quickly and easily. So, the whole reaction is determined by the second step,is the speed-controlled, i.e. the key step of the reaction. According to the calculated results, the activation energy is lower, react easily.2. The terminal substituents influence on the reactionDensity functional theory (DFT) has been used to study the influence of the reaction of 2.3-epoxy alcohols with different terminal substituents R( methoxyl, carboxyl, hydroxyl, amino),at the B3LYP/6-311+G (d, p) levels. The transition states and the energy barriers of the reactions are obtained.As a result, the substituents with strong ability for electronics have stimulative effect for the reactions.3. The influence of primary alcohol ,secondary alcohol ,tertiary alcohol for the reactionDensity functional theory (DFT) has been used to study the influence of the quantity of the carbon atoms in the position A at the B3LYP/6-311+G (d, p) levels.4. A DFT study for the mechanism of aza-Payne rearrangement reactionDensity functional theory (DFT) has been used to study the mechanism of the tow different aza-Payne rearrangement reaction at the B3LYP/6-311+G (d, p) levels. The transition states and the energy barriers of the reactions are obtained. The mechanism can be described by the following reaction sequences: The aza-Payne rearrangement can make the reaction route more flexible, product more changeable.5. The influence of THF solvent for the Payne rearrangement reaction.Density functional theory (DFT) has been used to compute the energy of the Payne rearrangement reaction of 2,3-epoxy butanol at the B3LYP/6-311+G (d, p) levels. As our calculation, inTHF solvent, the mechanism of the 2,3-epoxy butanol reaction is similar to the reaction in gas phase, the energy barrier in THF solvent is higher than that in gas phase.