Abstract
THE absorption spectra of methyl, ethyl, and isoamyl iodides consist, in the near ultra-violet, of broad continuous bands, with maxima at about 2550 A., and at high vapour pressures, a fairly well defined long wave-length limit at 3340 A. Undoubtedly this corresponds to dissociation into an excited iodine atom and an alkyl residue, and the process might be considered analogous to the disruption of hydriodic acid, HI. If we accept Mecke's figure (NATURE, April 5, 1930) for the energy of the C - H bond (115 kcal.) in hydrocarbons, there is very nice agreement between the thermochemical and spectroscopic data for the energy of the C - I bond. Using Berthelot's figures for the heats of combustion of the alkyl iodides, this energy is calculated to be 65 kcal. Allowing for the excitation energy of the I atom (21 kcal.), the spectroscopic figure is 64 kcal.
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IREDALE, T., MILLS, A. Energies of the C - I and G - Br Bonds. Nature 126, 604 (1930). https://doi.org/10.1038/126604a0
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DOI: https://doi.org/10.1038/126604a0
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