Pyrolysis of acetylene: a thermal source of vinylidene

We now report the results of kinetic and trapping experiments performed in acetylene/benzene and acetylene/toluene mixtures above 820 K by modulated beam dynamic mass spectrometry which provide direct evidence of vinylidene participation in chemical reactions. Under such conditions the fast equilibrium HC=CH ⇌ H_2C=C2^(2•) (1, -1) precedes carbene addition to the aromatic ring thereby circumventing kinetic restrictions arising from the short lifetime of vinylidene.