Photoionization mass spectrometry of 2-fluoropropane and 2,2-difluoropropane. A novel determination of the proton affinity of vinyl fluoride and 1,1-difluoroethylene

Journal Article · Wed May 12 00:00:00 EDT 1976 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00426a004· OSTI ID:7156677

Williamson, A D; LeBreton, P R; Beauchamp, J L

Photoionization efficiency curves for the parent and abundant fragment ions from 2-fluoropropane and 2,2-difluoropropane are reported in the energy region between threshold and 13 eV. For 2-fluoropropane an adiabatic ionization potential of 11.08 +- 0.02 eV is determined, with apparent thresholds of 11.23 +- 0.03, 11.53 +- 0.03, and 11.75 +- 0.03 eV for the fragment ions (CH/sub 3/)/sub 2/CF/sup +/, CH/sub 2/CHF/sup +/, and CH/sub 3/CHF/sup +/, respectively. For 2,2-difluoropropane an adiabatic ionization potential of 11.42 +- 0.02 eV is determined, with appearance thresholds of 11.57 +- 0.03 and 11.81 +- 0.03 eV for the fragment ions CH/sub 2/CF/sub 2//sup +/ and CH/sub 3/CF/sub 2//sup +/, respectively. These data are interpreted in terms of the thermochemistry of the neutrals and ions involved. From the difference in thresholds for the loss of CH/sub 4/ and CH/sub 3/, a thermochemical cycle yields the proton affinities of vinyl fluoride (173.6 kcal/mol) and 1,1 difluoroethylene (174.8 kcal/mol), independent of the heats of formation of any neutral species.

• Research Organization: California Inst. of Tech., Pasadena
• OSTI ID: 7156677
• Journal Information: J. Am. Chem. Soc.; (United States), Vol. 98:10
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
FLUORINATED ALIPHATIC HYDROCARBONS
PHOTOIONIZATION
MASS SPECTROSCOPY
HALOGENATED ALIPHATIC HYDROCARBONS
IONIZATION
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
SPECTROSCOPY
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