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| Paper |
Sara Boshamer
University of North Carolina at Asheville
Subject Listing - Chemistry
Advisor: Dr. Bert Holmes
Thursday, Oral Session 3, Presentation 2, Karpen Hall 038
EXPERIMENTAL INVESTIGATION OF THE UNIMOLECULAR REACTION PATHWAYS AND RATE CONSTANTS FOR ENERGIZED CF2ClCH2Cl
Hydrochlorofluorocarbons (HCFCs) are relatively stable, non-reactive, non-poisonous, and odor-free gases. These properties are why they are often used as refrigerants, aerosols, and as cleaning agents. However, HCFCs are dangerous in another way: they attack ozone molecules in the stratosphere. Therefore, it is important to study the decomposition reactions of HCFCs in the gas-phase to determine whether the products formed are safe for the environment. This research investigates the reaction pathways and reaction rate constants for a specific HCFC, 1,2-dichloro-1,1-difluoroethane (CF2ClCH2Cl). The CF2ClCH2Cl was prepared with about 95 kcal/mol of vibrational energy by the combination of CF2Cl and CH2Cl radicals. These radicals were generated by the UV photolysis of CF2ClCOCF2Cl and CH2ClI in clean quartz vessels. The reaction mixture was analyzed using a gas chromatograph/mass spectrometer (GC/MS) in order to separate and identify the reactant and products. The decomposition products observed by the GC/MS indicate that CF2ClCH2Cl undergoes 2,1-HCl elimination forming CF2=CHCl, 2,1-HF eliminations forming E- and Z-CFCl=CHCl, and a novel 1,2-FCl interchange reaction forming CFCl2CH2F. In addition, collisions may remove the internal energy forming a stabilized CF2ClCH2Cl. The product ratios of these molecules give rate constant ratios of 20:1:1:0.2 for the 2,1-HCl elimination reaction, E- and Z-2,1-HF elimination reactions, and the 1,2-FCl interchange reaction, respectively.
Advisor: Dr. Bert Holmes, Carson Distinguished Professor in the Sciences, Department of Chemistry, University of North Carolina at Asheville, Asheville, NC