Multi-channel Bond Breaking Theoretical Study Of Electron Transfer Reactions

In this paper, a reliable Density Functional Theory (DFT) method of B3LYP is employed to investigate three important reaction systems in atmospheric chemistry, and the reaction mechanisms is elucidated using the vibrational mode analysis. A new approach to empirically estimate the energy barrier between an intermediate (1M) and a transition state (TS) is also put forward.The whole paper consists of eight chapters. The first part summarizes the development of electron-transfer theory and the main aims of this paper. The second chapter introduces the elementary theory of the bond-rupture electron-transfer theory and its status quo of development. The main theoretical computation methods of quantum chemistry including ab initio molecular method and DFT are described in the third chapter. The fourth chapter introduces the harmonic oscillator model, normal mode vibration types and frequency characteristics of infrared spectra.On the basis of these theories, using vibrational mode analysis, the reaction mechanisms of three multi-channel free-radical reactions are studied extensively, and the relationships between the vibrational frequencies and potential energies as well as configurations are elucidated. The fifth chapter investigates the CHjO + CO reaction system, and gets the two energetically most favourable pathways, which are that CHjO and CO combine together to form IM1, and then IM1 produces CHs+CO: via TS4or TS3-IM2-TS6. The sixth chapter testifies that the main products ofthe multi-channel O (3P) + CHC1F system are Cl + CHFO and HC1 + FCO.According to the reaction mechanism of the open-shell reaction system of O (3P) + CHC1F, the seventh chapter is to reveal the relationship of energy barriers and the vibrational frequencies between IMs and TSs. In the adiabatic process, we suppose that the IMs are activated to the TSs. and the energies are not emitted into the surroundings but transform between the potential energies and the energies of motion, which are represented by the vibrating of atom groups. As a result, the values obtained from vibrational frequencies are in good agreement with the computational ones.In the eighth chapter, the reaction of hydrogen atom and the acetonitrile is studied and all possible reaction channels are found out.When using vibrational mode analysis to elucidate reaction mechanisms, we find that the only imaginary frequency of a transition state is always related to the breaking or forming bond that is extended. If the configuration of a species changes, it is certain that its frequencies should change accordingly, so using the vibrational mode analysis to elucidate the reaction mechanism is reasonable. If a bond is weakened, its frequencies are red-shifted, namely move to the lower region; Likewise, if it is strengthened, its vibrational frequencies will blue shift to the relatively higher frequency region.