Hydrogen atom abstraction by radical cations. The reactions of 9-substituted acridine radical cations with cyclohexa-1,4-diene

9-Substituted acridine radical cations undergo facile hydrogen atom abstrac tion reactions with cyclohexa-1,4-diene in dichloromethane-Bu4NPF6 (0.2 M): The kinetics of the reaction were studied by derivative cyclic voltammetry and observed to conform to the EC mechanism (charge transfer followed by i rreversible first-order reaction). The products of the reactions are the pr otonated acridine substrate and dimer-substrate adducts of cyclohexa-1,4-di ene. A comparison is made between the reactions of 9-phenylacridine and 9-p henylanthracene radical cations. The former undergoes rapid hydrogen atom a bstractions, while the latter slowly dimerizes in the absence of nucleophil es. It is suggested that localization of the odd electron in a p-orbital on nitrogen imparts the hydrogen abstraction activity of the radical cation. Since there are no free p-orbitals on the carbon atoms of the aromatic ring s in arene radical cations the hydrogen atom abstraction reaction pathway i s not observed.