Cation radicals, symbolized M • +, are usually generated by removing an electron from a neutral, electron-paired molecule. Thus they have both a positive charge and an unpaired electron. They are familiar as transient species in mass spectrometry, and they appear as by-products of electron emission in photoelectron spectroscopy. Several rather stable cation radicals, such as that from thianthrene (1) and , , ', 'tetramethyl-p-phenylenediamine (2) have been studied by electron spin resonance spectroscopy.1 However, the chemical reactions of cation radicals have not, until recently, received much attention. 1 2Cation radicals generated by chemical reactions in solution are normally in a thermally equilibrated condition, whereas those produced in mass spectrometry by high-energy electron impact are in electronically and vibrationally excited states.2 Nevertheless, mass spectrometric and photoelectron spectroscopic studies3 teach a lesson that is also relevant to solution chemistry, namely, that molecules containing "lone-pair" atoms such as O, N, or S are particularly prone to lose electrons. Cation radicals in solution are commonly obtained from oxidation of amines, sulfides, or oxygen compounds.The tris (p-bromophenyl) aminium ion 4 played a prominent role in our research, and its synthesis4 is illustrative. In 1:1 CH8CN-CF3COOH the oxidation-4 Xmax 725, 360 nm log «max 4. 52, 4.32 reduction potential of the reversible system, 3-4 is + 0.762 V, vs. Ag-AgClCh,6 and we have found that hexachloroantimonate ion, which has oxidizing charac-Anthony Ledwith was born in Wigan, England, in 1933, and is now a Senior Lecturer in Chemistry at the University of Liverpool. He graduated from the University of London and received his Ph.D. from the University of Liverpool. He was appointed to a lectureship at the University of Liverpool in 1958 and was awarded a D.Sc. by this University in 1971. Dr. Ledwith's research interests are in the general area of reactivity and mechanism with the particular objective of correlating well-known principles of physical organic chemistry with reactivity in polymeric systems.
