Abstract
Majer and Patrick1 have recently reported a value for the heat of formation of CF2 which differs appreciably from that reported by Margrave et al.2 and regresses toward values from the older literature. This heat has been deduced from electron impact studies on C6H5CF3 and C6H4FCF3 and involves the appearance potentials of the C6H5F+ and C6H4F2+ ions, respectively. Since those ions are not formed directly from the parent molecules, it is obviously dangerous to utilize appearance potentials for thermochemical calculations of any except the most qualitative nature, and a detailed consideration of the data seems to indicate that − 17 kcal/mole is only a positive limit for the heat of formation of CF2.
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References
Majer, J. R., and Patrick, C. R., Nature, 192, 866 (1961).
Margrave, J. L., J. Chem. Phys., 31, 1432 (1959). Brewer, L., Margrave, J., Porter, R., and Wieland, K., J. Phys. Chem., 65, 1913 (1961).
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J.A.N.A.F. Thermochemical Tables, edit. by Stull, D. R., March 31, 1961.
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MARGRAVE, J. Heat of Formation of the Difluoromethylene Radical. Nature 197, 376 (1963). https://doi.org/10.1038/197376a0
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DOI: https://doi.org/10.1038/197376a0
