Chlorine abstraction from arenesulphonyl chlorides by substituted phenyl radicals

Abstract

The relative reactivities of p-methoxy- and p-nitro-phenyl radicals (produced by iododediazoniation of the corresponding arenediazonium tetrafluoroborates) towards substituted benzenesulphonyl chlorides have been determined in competition experiments at several temperatures. The p-methoxyphenyl radical is more selective than p-nitrophenyl, but both show a small tendency to behave nucleophilically. The effect of substituents on the benzene ring of the arenesulphonyl chloride is of secondary importance, in accordance with the early transition state and the fact that sulphonyl radicals are not appreciably stabilized by delocalization over the ring.²

Relative Arrhenius activation energies and pre-exponential factors, determined from the relative reactivities, do not correlate with the polar characteristics of the substituents but may combine together to give relative rates which yield good Hammett correlations (in the case of p-methoxyphenyl radicals).