Mechanistic And Kinetic Studies Of The Reactions Of Halogenated Olefins With Radicals

Using the quantum chemical method, we systematically studied the mechanism asdkinetics of a series of the reactions of unsaturated alkenes with free radials （O（3^P）+CH₃CFCH₂, CF₃CHCH₂+OH and CH₂CHCH₂Cl+F） for the first time. The presenttheoretical study is helpful for the understanding the characteristics of the unsaturated alkeneswith free radials.The important and valuable results in this thesis are summarized as follows:1. The reaction of CH₃CFCH₂with O（3^P）The triplet potential energy surface of the O（3^P）+CH₃CFCH₂reaction has beeninvestigated at the BMC-CCSD//MP2/6-311++G（d,p） level. The results shown that thereaction proceeds via two mechanisms: hydrogen abstraction and addition/elimination. Theaddition/elimination channels are important thermodynamically and kinetically. MultichannelRRKM theory and transition-state theory are employed to calculate the rate constants over awide range of temperatures and pressures. The total rate constants show positive temperaturesdependence and pressure independence. The calculated overall rate constants are in goodagreement with the available experimental data.2. The reaction of CF₃CHCH₂with OHThe potential energy surfaces of the CF3CH=CH2+OH reaction have been investigated at theBMC-CCSD level based on the geometric parameters optimized at the MP2/6-311++G（d,p）level. Various possible H （or F）-abstraction and addition/elimination pathways are considered.Temperature and pressure dependent rate constants have been carried out usingRice-Ramsperger-Kassel-Marcus theory. The calculated results are in good agreement withavailable experimental data.3. The reaction of CH₂CHCH₂Cl with FThe complex potential energy surfaces for the reaction of atomic radical F withCH₂CHCH₂Cl are explored at the CCSD（T）/cc-pVTZ//MP2（full）/6-311++G（d,p） level. Thereare various possible reaction pathways including the addition-elimination and H-abstractionreaction. Among them, the most feasible pathway should be to produce CH₂CHCH₂F+Cl,which is in good agreement with the experiment. Among the H-abstraction reactions, the mostcompetitive pathway is the atomic radical F abstracting hydrogen atom from allylic group.Because all of the transition states and intermediates involved in the title reaction lie belowthe reactants, the F+CH₂CHCH₂Cl reaction is expected to be rapid.