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Wednesday, April 26 • 2:00pm - 2:20pm
Investigation Of The Competitive Unimolecular Reactions Of Chf2chf2 And Chf2cf3

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Amendments to The Montreal Protocol have called for a phase out of all hydrochlorofluorocarbons (HCFC’s) and hydrofluorocarbons (HFC’s). These common gases are found in many household appliances such as refrigerators and air conditioners. Little is known about the 1,1-HX (X=halogen) elimination channel of HFCs; thus, we have designed a number of model compounds to learn more about the kinetics and mechanism of 1,1-HX elimination reactions. Here we present experimental and computational results for chemically activated CHF2CHF2 (HFC-134) and CHF2CF3 (HFC-125). The carbene from CHF2CHF2 has previously been reported to isomerize to CHF=CF2, but our calculations show that the isomerization barrier is too high. The carbene yield was measured by trapping with trans-2-butene. The 1,2-HF and 1,1-HF elimination rate constants were experimentally determined to be 4.6 x 105 s-1 and 1.3 x 105 s-1, respectively. The same method has been used to measure the 1,1 HF and 1,2 HF elimination rate constants of CHF2CF3. A variety of computational methods and basis sets were explored to find the 1,1 HF and 1,2 HF transition states and threshold energies for both compounds. A CF2 expulsion reaction pathway to yield fluoroform has also been identified in CHF2CF3.


Wednesday April 26, 2017 2:00pm - 2:20pm PDT
014 Zeis Hall