Radical Addition Reactions

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DR. BARTON‘S term ‘high differential electron density' is quite useful for explaining more precisely my early, and vague, statement that "free radicals attack molecules preferentially at points of high electron density"1. Obviously electron-availability is an essential requisite for free radical reactions. Free neutral radicals, such as Br·, CH3·, or C6H5·, are electrophilic reagents in so far as they tend to complete their electron octets, and this end they can achieve (a) by combining with another unpaired electron, as in CH3· + ·NO − CH3· − NO; (b) by combining additively at one of the easily available Ï-electrons of an olefinic bond; or (c) by abstracting an outer atom plus one electron from another molecule, as in Cl· + HCH3 ’Cl’ H + ·CH3. The case of reaction is a > b > c, and this is the order of available electron densities at the atom which is attacked.

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  1. 1

    Waters, Trans. Farad. Soc., 37, 770 (1941).

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WATERS, W. Radical Addition Reactions. Nature 162, 183 (1948) doi:10.1038/162183a0

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