Iodoalkanes Iodomethanes

Oxidation of iodoalkanes involves removal of an electron from the halogen nonbonding orbital. The radical-cations of primary and secondary alkyl iodides can be identified in aqueous solution by their absorption spectra and have half-lives of microseconds [1]. They are formed during pulse radiolysis of the iodoalkane in aqueous solution in the presence of nitrous oxide. This system generates hydroxyl radicals, which remove an electron from the iodine atom lone pair. Iodoalkane radical-anions complex with the lone-pair on other heteroatoms to form a lollo three-electron bond. In aqueous solution, the radical-cation of iodomethane is involved in an equlibrium indicated by Equation 2.1. 

The simplest iodoalkane, CH3I, has been studied repeatedly by MW and ED (Table 43). The re value for the C—I distance from a combined MW/IR investigation and the rg value which is reported in a recent ED analysis of the entire series of the iodomethanes CH I, n = 1 to 4, are in perfect agreement. The gas-phase studies for the methanes with two or more iodines were performed at 360 K for CH2I2, at 400 K for CHI3 and at 425 K for CI4. Within the combined experimental uncertainties the C—I bond distances remain constant for mono-, di- and triiodomethane and increases by ca 3 pm in carbon tetraiodide. As in the case of carbon tetrachloride and tetrabromide, this increased bond length in CI4 can be rationalized by steric repulsions between the iodine atoms. The large steric requirement of... 

Paquette, J., Ford, B. L. The radiation-induced formation of iodoalkanes and the radiolysis of iodomethane. Proc. 2. CSNI Workshop on Iodine Chemistry in Reactor Safety, Toronto, Can., 1988 Report AECL-9923 (1989), p. 48-73 Paquette, J., Sunder, S., Torgerson, D. F., Wren, C. J., Wren, D. J. The chemistry of iodine and cesium under reactor accident conditions. Proc. 3. BNES Conf. Water Chemistry in Nuclear Reactor Systems, Bournemouth 1983, Vol. 1, p. 71—79 Parsly, L. F. Chemical and physical properties of methyl iodide and its occurrence under reactor accident conditions. Report ORNL-NSIC-82 (1971)... 

An investigation (113) of the Tg of the poly(styrene-co-vinylpyridine) copolymers quatemized with iodoalkane found that the Tg increased with increasing ion content, but that the increasing rate of the Tg with ion contents (dTg/dc) depended on the length of an alkyl chain. For example, dTg/dc for the ionomer quatemized with iodomethane was ca 3.2°C/mol%, while for the ionomer quatemized with iododecane it was only ca l.l°C/mol%. 

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