Polar effects in free radical reactions. Homolytic aromatic amination by the amino radical cation, ·+NH3: reactivity and selectivity

Small amts. of Fe(II) salt initiate redox chains with H2NOSO3H and arom. compds., leading to the amination of the arom. ring. The positional and substrate selectivities with a variety of substituted benzenes show the important role of the electrophilic character of •+NH3. Hammett relations with σ and σ+ are roughly obsd. The lower sensitivity to polar effects of •+NH3, compared with Me2NH+• is explained by the different reaction enthalpies. The different positional selectivity obtained with anisole and the redox system +NH3OH/Ti(III) is discussed