Aromatic compounds, fused radical alkylation

The fact that most alkylated benzenes show the same tendency to soot is also consistent with a mechanism that requires the presence of phenyl radicals, concentrations of acetylene that arise from the pyrolysis of the ring, and the formation of a fused-ring structure. As mentioned, acetylene is a major pyrolysis product of benzene and all alkylated aromatics. The observation that 1-methylnaphthalene is one of the most prolific sooting compounds is likely explained by the immediate presence of the naphthalene radical during pyrolysis (see Fig. 8.23). 

The photolysis of nitrosopregnone steroid (117) afforded the 18,20-benzo-fused compound (118) as the major product (24%) along with the diol (119) (6%), whilst the expected C(18) rearranged product (120) is not isolated (Scheme 17).277 Reaction proceeds via the C(18) alkyl radical (121), formed in accordance with the accepted C(ll) O—NO bond homolysis and H-abstraction pathway, before either addition of C(11) radical (121) to the aromatic ring to afford (118) or H abstraction to give (119). 

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