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Theoretical Studies on the Reaction Mechanisms of Several Radicals with CF3 OCHF2 and CHF2 OCHF2

Author: YuYanBo
Tutor: PanXiuMei
School: Northeast Normal University
Course: Physical and chemical
Keywords: Reaction mechanism Potential energy surfaces Transition state HFEs
CLC: O643.12
Type: Master's thesis
Year: 2011
Downloads: 16
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Abstract


Hydrofluoroethers （HFEs） are being used as third generation replacements to chlorofluorocarbons （CFCs） because of their nearly zero stratospheric ozone depletion and relatively low global warming potential. HFEs have been used in various industrial applications. From the environmental, ecological, and health points of view, it is important to understand their environmental risks for these HFEs from a diversity of commercial applications and industrial processes. Therefore, in order to better assess the atmospheric and environmental impact of HFEs, the mechanisms and kinetics of the HFEs with radicals have been studied deeply by many theoretical investigations. They are very important to control atmospheric pollutions.The quantum chemistry methods were used to investigate the reaction mechanisms of CF3OCHF2 + O（1D） reaction. Using ab initio and density function theory （DFT） chemistry methods, we studied the the detailed mechanisms and rate constant of CHF2OCHF2 + Cl. Thus, useful information and elementary theoretical evidence are provided for further studying these reactions experimentally.The results of this work are summarized as follows:1. The theoretical study on the of CF3OCHF2 + O（1D） reaction are investigated deeply using DFT （B3LYP） and MC-QCISD methods with 6-311G（d,p） basis set. The geometries, vibrational frequencies and the singlet point energy of all stationary points on potential energy surfaces （PESs） are obtained. Standard enthalpies of formation of CF3OCHF2 are estimated theoretically using group-balanced isodesmic reactions （Ra-Rc）. Moreover, The reaction enthalpies of the major reaction channels are calculated. The results show that seven different intermediates are located at the reactant side by three initial association ways: i.e. insertion into C-H bond, insertion into C-O bond, or addition to the F atom of CF3OCHF2, respectively. There are five reaction pathways are feasible and five products may be obtained. Among them, P2, P, and P4 are primary products, while P1 and P5 are minor products.2. The theoretical investigation on the H-abstraction reaction mechanism of the reaction CHF2OCHF2 + Cl. The optimized geometries and harmonic frequencies of the reactants, products, hydrogen-bonded complex and transition states are obtained at the G3MP2//UMP2/6-311G（d,p） level for the H-abstraction reaction mechanism of CHF2OCHF2 + Cl. The results are consistant with the available experimental data. Standard enthalpies of formation of CHF2OCHF2 radical are estimated theoretically using group-balanced isodesmic reactions. We hope our calculation may be useful for gaining insight into the mechanism and may provide useful information for future experimental studies of the title reaction.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Chemical kinetics > The mechanism and kinetics of chemical reactions
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