Chemically activated CD3CHFCl was prepared with approximately 90 kcal mol-1 of vibrational energy by the combination of CD3 and CHFCl radicals.  The radicals were generated by the mercury photosensitization of mixtures containing CD3I, CHFCl2 and CF3CH=CH2 as a radical trap.   The reaction products were analyzed by GC/MS to measure the CD2=CHF/CD2=CDF (m/z = 48/49) and CD2=CHCl/CD2=CDCl (m/z = 66/67).  The ratio of vinyl fluoride-d2/-d3 is the branching ratio for 1,2-DCl/1,1-HF and the vinyl chloride-d2/-d3 is the branching ratio for 1,2-DCl/1,1-HCl.  The CD2=CHF/CD2=CDF was 2.5 at the highest pressures and became constant at 1.9 for pressures greater than 2 Torr.  Accounting for the expected isotope effect for 1,2-DCl/HCl elimination of 3 shows that the branching ratio favors the 1,2-HCl loss by a factor of 6 compared to 1,1-HCl elimination for CD3CHFCl.  Data for the CD2=CHCl/CD2=CDCl declined from about 8 at the highest pressures to 0.5 at the lowest pressures.  This data, when the normal isotope effect for 1,2-DF/HF is included, suggests that the 1,1-HF elimination channel nearly equals the 1,2-HF channel.  This large contribution from the 1,1-HF pathway for CD3CHFCl is surprising.

Experimental measurement of the branching ratio for the competitive 1,2-DF/1,1-HF and 1,2-DCl/1,1-HCl unimolecular elimination from CD<sub>3</sub>CHFCl

247th National Meeting (2014)

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Experimental measurement of the branching ratio for the competitive 1,2-DF/1,1-HF and 1,2-DCl/1,1-HCl unimolecular elimination from CD3CHFCl

Experimental measurement of the branching ratio for the competitive 1,2-DF/1,1-HF and 1,2-DCl/1,1-HCl unimolecular elimination from CD₃CHFCl