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The Theorical Study on the Formation about β-CD-Styrene Oxide and β-CD-N-Tosyl-2-Phenyl-Aziridine, and HBr-Induced Ring Opening of Styrene Oxide in the Presence of β-CD

Author: FanFang
Tutor: YangZuoYin
School: Beijing University of Chemical Technology
Course: Chemistry
Keywords: β-CD Styrene oxide 2 - phenyl-N- tosyl aziridine (NT2PA) Supramolecular systems Quantum chemistry Reaction Mechanism Ring-opening reaction
CLC: O621.13
Type: Master's thesis
Year: 2010
Downloads: 32
Quote: 0
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Abstract


p-cyclodextrin (p-CD) through the interaction between the main object and the organic molecules transferred to the organic reaction to environmentally friendly aqueous solvent, and the reaction can be obtained in good yield under mild conditions, so p -CD is widely used in the green organic synthesis. However, the lack of theoretical discussion of such catalytic reaction mechanism of p-CD. This paper uses quantum chemical calculations of the p-CD-styrene oxide, p-CD-2-phenyl-N-tosyl aziridine (NT2PA) supramolecular systems theory to examine p-CD with HBr directional ring-opening reaction mechanism to reveal the nature of the high selectivity and experiments provide guidance reference. Firstly, using quantum chemistry methods to study the formation process of the p-CD-styrene oxide, β-CD-NT2PA supramolecular systems. The results show that the Styrene oxide, NT2PA are will be inclined to take the phenyl toward the direction of the p-CD small mouth into the lumen, this way is more conducive to the stability of the system energy, and the dipole moment and the energy to change the same regularity described dipole interaction is an important factor for promoting the guest molecules into the lumen of the p-CD. The charge topology analysis found the two clathrate system, the guest molecule of O, N atom with a hydroxyl group of p-CD big mouth edge can form hydrogen bonds, i.e. guest molecules in the p-CD phase having a specific orientation. Therefore styrene oxide, NT2PA the positioning of the role of p-CD is mainly due to the strong dipole interactions and hydrogen bonding interactions between the main guest molecules. This article also uses quantum chemical methods to the study of a free state, styrene oxide with HBr reaction mechanism. The results showed that there are two possible reaction path: step-by-step reaction mechanism and concerted reaction mechanism in the free state, styrene oxide reacts with HBr. Step-by-step reaction mechanism, protons first attack the oxygen atom to form a carbocation intermediate bromine anion with carbon positive ions is then combined to give the 2 - bromo - 2 - phenyl ethanol, and the reaction No barrier; concerted reaction mechanism, the product with the Proton and bromine anion is close to the orientation of the reactants varies, and the whole process is also no barrier. Given by the reaction mechanism of a free state where the styrene oxide with HBr and the experimental results of β-CD-styrene oxide with HBr reaction mechanism may be synergistic reaction mainly i.e. strong dipole interaction, a bromine anion only in a particular direction into the internal cavity of the β-CD.

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