Thermodynamic stabilities of carbon-and nitrogen-centered radicals

The gas-phase homolytic C-H and N-H bond dissociation energies(BDE)of the substi-tuted phenoacetonitrile families,aromatic amines,and semicarbazone derivatives were systematically investigatedor reinvestigated based on a cycle utilizing the thermodynamic quantities determined in DMSO solution.Theexperimental evidence collected in.this work dearly indicates that the radicals derived from the above familiesare of the‘Class O’type,i.e.to be stabilized by a remote electron-donating substituent but destabilized by anelectron-withdrawing substituent.