Vinyl double bonds reaction with secondary radicals

Reaction of vinyl double bonds with secondary radicals. 

The mechanism of formation of the initial benzene molecule in combustion of hydrocarbons depends on both the fuel and the reaction conditions. Two classes of ring-forming reactions have been proposed. The first class involves addition of acetylene to vinyl-type radicals (i.e., short-chain radicals containing a double-bond), with subsequent cyclization to a five or six membered ring, depicted in Fig. 14.8. In these reactions the adduct does not require intramolecular rearrangements prior to cyclization [318]. However, under most conditions these reactions are thought to be of secondary importance. 

---