ABSTRACT
In chemistry (not to speak of biology), free radicals (i.e., species with an unpaired electron or, in other words, compounds containing a three-valent carbon atom) were considered to be freaks, if they existed at all, because the four-valent carbon atom is an obligatory element of all organic compounds. However, the existence of free radicals became a proven fact when in 1900 Moses Gomberg reported his results on the reaction of triphenylmethyl halides with metals. The yellow reaction product was identied as free triphenylmethyl radical Ph3C. This radical was a stable compound due to the delocalization of an unpaired electron on three phenyl groups. However, already in 1929, F.A. Patheth and W. Hofeditz demonstrated in their classic experiment that highly reactive methyl radicals were formed when the vapors of tetra methyllead, Pb(CH3)4, were mixed with gaseous hydrogen during its passage through a silica tube.
