Evidence for the electrophilic character of the toluene-p-sulphonyl free radical: relative rates of its addition to some substituted styrenes

Abstract

Relative rates of photochemically promoted additions of toluene-p-sulphonyl iodide to styrene and four of its derivatives have been measured in benzene solutions containing picric acid to inhibit concurrent polymerisation. Electron-attracting substituents in the Ar group of Ar·CH:CH₂ retard the rate of addition of Tol·SO₂· to the double bond. With reference to σ⁺(Brown)ρ is estimated as –0·50 and with reference to σ(Hammett) as –0·55.