Hydrogen atom transfer trapping intermediates

I, 4-dehydrobenzene intermediates. Trapping by inter- and intramolecular hydrogen atom transfer and observation of high-temperature CIDNP. 

Hydrogen-transfer Reagent in Radical Reactions. Thiols, in particular tertiary mercaptans such as tert-butanethiol and triethylmethanethiol, have been widely used in radical reactions to trap radical intermediates by hydrogen atom transfer. ferf-Dodecanethiol is a vahd substitute for those mercaptans, since it is cheap, relatively odorless compared to the other alkanethiols, and generally equally efficient with respect to the hydrogen donor properties. 

As to the next step, namely, the reaction of aryl radicals with nucleophiles, we should take into account the fact that air molecular orbital, which initially accommodates the incoming electron, is available in the aryl halide. The electron is subsequently transferred in-tramolecularly from the it to the o molecular orbital of the carbon-halogen bond. Aryl radicals effectively scavenge H atoms. Therefore, an abstraction of a hydrogen atom from the solvent may occur. However, in the case of nucleophiles that can act as effective traps of aryl radicals, the addition of a nucleophile to the phenyl radical takes place. At this point, let us focus on the step of addition of the nucleophile (Y ) to the intermediate radical (Ph). When a new a bond begins to form between the sp3 carbon-centered radical (H5C6) and... 

FIGURE 7.1 Radical catalyzed oxidation of linoleic acid. X is used to represent a generalized radical sufficiently reactive to remove a bis-allylie hydrogen atom. YH is a generalized hydrogen source that can transfer H to -OO". The products in brackets are only observed when the intermediate products are rapidly trapped by H transfer. 

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