Unimolecular decomposition of CF3CHClCCl2 radicals chemically activated by the reaction of TCE and CF3 radicals.
Pagnareach Tin Dr. Bert Holmes The Department of Chemistry at University of North Carolina Asheville
Abstract Trichloroethylene (CHCl=CCl2) or TCE was widely used in the chemical industry due to its versatility and properties. The most common use for TCE is as a degreaser agent. Factories that produce products such as hearing aids used TCE to degrease metal components that were used in the production of hearing aids. Ever since TCE was banned by the Environmental Protection Agency (EPA) due to its carcinogenic properties, tons of TCE in used remained in the environment. A reaction between TCE and CF3 radicals was studied in order to determine possible pathways that TCE can react to form various products. Photolysis of CF3I was the source of CF3 radicals that subsequently added to the CHCl end of TCE producing chemically activated CF3CHClCCl2 radicals in the gas phase. The addition of CF3 radicals to the CCl2 end of TCE would produce CF3CCl2CHCl radicals, but quantum chemical calculations using Gaussian verified that this reaction was not important, in agreement with experimental findings. The chemically activated CF3CHClCCl2 radical decomposed by loss of atomic Cl to form CF3CH=CCl2 or was stabilized by collision with reactant molecules. The stabilized CF3CHClCCl2 radical combined with CF3 radicals yielding CF3CHClCCl2CF3. The atomic Cl added to TCE forming the CHCl2CCl2 radical that subsequently combined with CF3 radicals producing CHCl2CCl2CF3. Gas chromatography and mass spectra analysis were used to determine products that were formed in the reaction vessel. Three main products that formed were positively determined to be CF3CHClCCl2CF3, CF3CH=CCl2, and CF3CCl2CHCl2. Future studies include determining reaction pathway and characterizing final products of the reaction between CFCl=CFCl and CF3 radicals as well as trans-CHCl=CClCF3 and CF3 radicals.
