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Theoretical Study of Activation H-H σ Bond, C-H and C-C Bonds of Hydrocarbons by CrO2～+ in the Gas Phase

Author: ChenXiaoXia
Tutor: WangYongCheng
School: Northwest Normal University
Course: Physical and chemical
Keywords: Two-state reaction Activation of the H-Hσ key C-H bond and C-C bond The potential energy surface cross fragment molecular orbital theory
CLC: O641.1
Type: Master's thesis
Year: 2006
Downloads: 67
Quote: 1
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Abstract


In recent years, people found in the study transition metal vapor phase reaction the reactant (or intermediate) of the ground state and the product of the ground state has a different spin states. That does not comply with the spin conservation law. For example the the former transition metal ions Sc -V and their oxide and titanium oxide ion (VO 2 and CrO 2 ) reaction with H 2 O molecules. Due to flip the spin caused by the reactants and products which have a different spin states phenomenon in the solidification phase reaction is often ignored, that is a spin-forbidden reaction. Despite more than a decade ago has been proposed potential energy surface of the cross is a two-state reaction of the fundamental mechanisms of saying, but due to the influence of the time of spin conservation law until 1994, with the development of high-tech experimental means, the entire reaction pathway , have been monitored type of reaction is indeed contrary to the spin conservation law. This potential energy surface of the cross was only slowly accepted the two-state reaction of the statement of the fundamental mechanisms. How to be more reasonable to explain these phenomena and to stimulate a more in-depth study of the reaction of the people on the two-state. In this paper, the transition metal dioxides the CrO 2 activated H-Hσ key CH bond of methane and ethylene CC key subject of quantum chemistry calculation means done some theoretical aspects research. Specific based on quantum chemistry, molecular orbital theory, transition state theory-based, using density functional theory (DFT) perturbation theory (MPn), coupled cluster method (CCSD (T)), fragments of molecular orbital theory (FMO choose the calculation basis set) and natural bond orbital (NBO) analysis method, the research system to find out the reaction of various species (including transition state) optimized geometries calculated, and thus the potential energy surface, the spectral data thermodynamic data and molecular orbital. We use these data and comprehensive analysis and interpretation of the reaction mechanism. The paper is divided into five chapters. The first chapter gives an overview of the development and application of this cutting-edge field of quantum chemistry, as well as the background and status of the two-state reaction theory, and their predecessors in the transition metal CH bond activation of the HH bond and hydrocarbons, CC bond in this field in nearly a decade of research status of a brief overview. Chapter II briefly introduces the basic theory and quantum chemical calculations, including the basic theory of quantum chemistry and reaction potential energy surface, the potential energy surface intersects with disjoint rules, intersystem crossing transition state theory, spin - orbit coupling mechanism and the Department of selection rules. The first two chapters are mainly summarizes the theoretical background and theoretical basis of this work, our study provides a reliable quantum chemical theoretical basis and the practical foundation. Chapter III, Chapters IV and V, we selected CrO 2 with the H 2 the CH 4 and C 2 H in 4 reaction system as the research object, analyzes the transition metal dioxide HH bond, the CH bond of methane and ethylene CC bond activation on a two-state reaction (TSR) conducted in-depth research. First, the main use of charge-transfer, the natural bond orbital (NBO) analysis and molecular orbital theory in combination with other analytical methods discussed most of the initial complex formation and nature. Second, the reaction path to do a simple description of the microscopic mechanism of the reaction at a glance. Third, first with Hammond assumptions to deduce the approximate location of the potential energy surface crossing, further use of the the Yoshizawa intrinsic vertical coordinate single point excited state cross-point (CP) method to determine the potential energy surface structure and relative energy, and finally discuss its for The reaction efficiency and the reaction rate of the overall reaction. Fourth, the use of fragments of molecular orbital theory, [the fragment Molecular ORBITAL (FMO)] corresponding to the transition states of molecular orbital interaction analysis, further explanation of the two oxides of the transition metal CrO 2 activated H-Hσ bond, CH bond and CC bond mechanism.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Structural Chemistry > Chemical bond theory
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