Abstract
THE ethylene linkage in the aliphatic hydrocarbons is characterised by two ultra-violet bands; an intense one 1800–1900 A., and one of low intensity between 2200 and 2600 A. (Stark et al., Jahr. Rad., 10, 139; Luthy, Zeit. Phys. Chem., 107, 285; Carr, J. Am. Chem. Soc., 51, 3041). The thermal equivalents (Nhν) of the two middle positions are 154.0 and 118.8 Kcal. and the difference is 35.2 Kcal.; this is almost identical with the difference in heats of combustion between a saturated hydrocarbon and the corresponding olefine, which for the first five members of the series is 36.8, 36.1, 36.2, 39.9, 37.2 Kcal. (Kharasch, Bur. Stand. Jour. Research, 2, 359). The average value for the thermochemical characteristic of the C-C and C-H linkage in the liquid state is 52.1 Kcal. The heat of combustion of an hydrocarbon (liquid state) containing m double bonds can be represented by where ν1 and ν2 are the centres of the absorption bands. For example, Q, calculated from Stark's data for diallyl, is 926.7 Kcal.; experimental, 921.1.
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CARR, E. A Relation between Ultra-violet Absorption Spectra and Heats of Combustion. Nature 125, 237 (1930). https://doi.org/10.1038/125237a0
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DOI: https://doi.org/10.1038/125237a0
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