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Silylene into the reaction in the three-dimensional electronic effects

Author: JinJuan
Tutor: QiuHuaYu
School: Hangzhou Normal University
Course: Organic Chemistry
Keywords: Silylene Insertion reaction Three - dimensional electronic effects Quantum chemistry Density functional
CLC: O627.41
Type: Master's thesis
Year: 2010
Downloads: 43
Quote: 0
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Abstract


In this paper, three different Silylene (1-3, Scheme 1) containing different substituents chlorosilane and silane insert the reaction theoretical research model, systematic study of them occurred Si-Cl and Si-H Insertion reaction mechanism, the difference between the two reaction types and affect the reaction rate and selectivity of the main factors to investigate the reaction mechanism of silylene with silane insertion reactions, but also research the Silylene and halogen silane Si- X (X = F, Cl, Br) is inserted in the relative activity of the reaction, simultaneously Silylenoid 4 and the type of reaction of the silane through experiments carried out on the theoretical results of the validation. The main research methods used in this paper: quantum chemistry density functional theory (B3LYP) use Gaussian98/03 program, 6-31 G (d, p) basis set of stationary points on the reaction potential energy surface structure Full optimization type. The main research include: 1. Occurred on the the dimethyl Silylene with a chlorosilane Si-Cl insertion reaction mechanism studies show that the insertion reaction by the synergistic mechanism of the final product with a three-membered ring transition state. Especially worthy of our attention in the study found that the insertion reaction activity Silylene size silane substituents have the three-dimensional electronic effect relationship. The silane substituent in the transition state, there are two types, with a three-membered ring transition state in the same plane, mainly for electronic effect. The study found that suck the electronic effect of the substituent can greatly improve the reactivity, and for the electrons will reduce the reactivity of substituents; another with the three-membered ring in the same plane, mainly for steric effects. The study found that the large steric hindrance of the substituents will reduce the activity the silylenoids Si-Cl and Si-H insertion reaction, but the impact is greater than the Si-Cl insertion reaction of Si-H insertion reaction. Comparing the electronic effects and steric hindrance, and found that the electronic effect factors to be greater than the steric effect. 2. Visits silicon-substituent on the insertion reaction. Studies have shown that with optimum HsSiCl, and H3SiH by by containing different sterically hindered silicon ene (Silylenoid, 1-3) and with different electronegativity substituent Silylenoid respectively reaction pathway for the insertion reaction of Si-Cl and Si-H steric hindrance on Silylenoid will also reduce insertion reaction activity, but with a steric effect on the silane type, quite the silylenoids steric effect of the Si-Cl and Si-H insertion reaction, while a silane steric effect of the two reactions is unequal, the impact of its Si-Cl insertion reaction is greater than the Si-H insertion reaction. While the type and the electronic effect of the substituent on the silane is electron-withdrawing group on the Silylenoid it will weaken the activity of the reaction, the reaction is not easy to carry out. 3. Visits silicon-halogen silane Si-X insertion reaction activity occurs. Si-X (X = F, Cl, Br) through the of dimethyl Silylenoid series of halosilanes occur insertion reaction of the Si-Br insert the activation energy of the reaction to be significantly smaller than the other Si-X insert, for the same a silane containing Si-F, Si-Br, Si-C1 key, the Si-Br insertion occurs preferentially. 4 targeted design validation experiments, 2,2,5,5 - tetrakis (trimethylsilyl) cyclopentyl Silylene and the type of chlorosilanes role, theoretical results according to the reaction of the resulting product The silane steric electronic effects Silylene insertion reaction has been verified. The study established on Silylene and silane Si-H and Si-X insertion reaction in a series of new reaction mechanism, make a reasonable explanation for the experimental phenomenon on theoretical calculation results with the experimental be verified. The results of their research not only for theoretical workers provide a theoretical basis, and further study of this subject for experiments workers effectively develop and use silylene insertion reaction to synthesize new organic silicon compounds has important application value in the field of materials, synthesis of pharmaceuticals and other scientific and polymer provides the theoretical basis of the system.

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CLC: > Mathematical sciences and chemical > Chemistry > Organic Chemistry > Elements in organic compounds > The first IV group elements, organic compounds , > Silicon organic compounds
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