REDOX AND ACIDITY PROPERTIES OF ALKYLAMINE AND ARYLAMINE RADICAL CATIONS AND THE CORRESPONDING AMINYL RADICALS

In this work the pK(a)s of six alkyl- and arylamine radical cations in aqueous solution have been determined by means of laser flash photoly sis. The corresponding N-nitrosamines were used as precursors for the aminyl radicals which, upon protonation, formed the amine radical cati ons. The following pK(a)s were obtained: 3.6 +/- 0.2, 7.6 +/- 0.3, 6.8 +/- 0.5, 5.3 +/- 0.5, 5.5 +/- 0.5, and 5.8 +/- 0.5 for the radical ca tions of diphenylamine, N-methylaniline, dimethylamine, diethylamine, pyrrolidine, and piperidine, respectively. In addition, the peak oxida tion potentials of diphenylamine, N-methylaniline, aniline, diethylami ne, pyrrolidine, and piperidine have been measured in aqueous solution and in acetonitrile using cyclic voltammetry. Furthermore, the one-el ectron reduction potentials of the diphenylaminyl radical and the N-me thylanilinyl radical in acetonitrile were measured using photomodulati on voltammetry. The results of this study and of previously published studies are discussed in terms of relative substituent and solvent eff ects.