Kharasch side-reactions

Diaryls. A dil. soln. of o-iodophenol in benzene irradiated 20 hrs. in a Vicor -7100 tube by a cold-cathode low pressure Hg-lamp until the release of iodine, as measured by titration with thiosulfate, is complete 2-hydroxybiphenyl. Y 60-70%.—Side reactions are minimized by conducting the reaction at or near room temp, and using monochromatic UV-light which cleaves only the carbon-iodine bond. F. e. s. W. Wolf and N. Kharasch, J. Org. Ghem. 26, 283 (1961). 

Halogenation of alkanes had long been known, and in 1930 the kinetics of the chlorination of chloroform to carbon tetrachloride were reported by Schwab and Heyde (equation 40), while the kinetics of the chlorination of methane were described by Pease and Walz in 1931. Both of these studies showed the currently accepted mechanism, which was extended to reactions in solution by Hass et al. in 1936. The free radical halogenation mechanism of other alkanes was described by Kharasch and co-workers, ° including side chain halogenation of toluene. 

Effect of Oxidants, Kharasch has shown that, in the presence of benzoyl or other organic peroxides, sulfuryl chloride selectively chlorinates the side chain and not the nucleus of alkyl-substituted benzene. The reaction, which is carried out in the dark, is also useful for the chlorination of aliphatic compounds such as acyclic hydrocarbons, cycloparaflSns, carboxylic acids, and their acid halides. ... 

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