The Oretical Study On The HBr-Induced Ring Opening Of Styrene Oxide In The Presence Of β-CD

The primary quantum study on the HBr-induced ring opening of styrene oxide in the presence ofβ-CD is carried out, and the reaction process could be divivided into two following parts.On the one hand, The molecular dynamic simulation and quantum chemistry methods were employed to study the supramolecular systems ofβ-CD-styrene oxide andβ-CD-protonated styrene oxide. The results show that, when the phenyl group of protonated styrene oxide points to the secondary rim ofβ-CD, the system is inclined to be more stable and its attractive energy is relatively larger. But the case for styrene oxide is disagreement with the protonated partner. However, in the view of kinetics, the phenyl group of styrene oxide maybe finally point to the secondary rim ofβ-CD due to its comparatively less repulsive energy in the complex. The property of electron density analyzed by topological study indicates that hydrogen bond has formed between the host and guest molecules when the phenyl group of guest molecules points to the secondary rim ofβ-CD. As a result, it is suggested that the orientation effect on styrene oxide in the inner phase ofβ-CD might mostly be attributed to the interactions between the host and guest molecules, such as H-bond, dipole action, etc.On the baisis of the above,the reaction mechamism concering HBr-induced ring opening of styrene oxide in the presence ofβ-CD is investigated by quantum chemistry,compared to the reaction withoutβ-CD. It is possible that bromine anion and proton react sinutaniously either inner ofβ-CD or in the free condition,and the reaction without transition is neither S_N2 nor S_N1,meanwhile due to the primaryβ-CD dipole influence the reaction withoutβ-CD yield the only 2-bromine-2-phenylethanol in the presence ofβ-CD; Another reaction product is only 2-bromine-1-phenylethanol owing to styrene oxide intrinsic pole action in the free condition.