Anchimeric assistance in carbon-hydrogen bond homolysis. Reaction of tert-butoxyl radicals with tetraethyl Group IV compounds

Three complementary techniques have been used to obtain relative and absolute rate constants for the abstraction of α- and β-hydrogen atoms from (CH3CH2)4M (M = C, Si, Ge, Sn) by tert-butoxyl radicals. Both α and β positions of Et4M are activated for M = Si, Ge, Sn, as compared with the 1- and 2-positions in n-pentane. The activation was greater at the β than at the α position, and followed the order Sn > Ge > Si. This provides unequivocal evidence for anchimeric assistance to removal of hydrogen β to a Si, Ge, or Sn atom.