The reaction of sulphur dioxide with ethyl radicals, generated by the photolysis of diethyl ketone, has been studied in the temperature range 28–75°C. At low temperatures the addition reaction to form ethylsulphonyl radicals is rapid but the radicals become increasingly unstable as the temperature is raised.

Arrhenius parameters (based on a value of 10¹⁴ mole^–1 cm³ sec^–1 for the rate of combination of ethyl radicals) have been measured or deduced for the following reactions: [graphic omitted] A value of 0.05±0.04 has been obtained for the disproportionation: combination ratio of ethyl and ethylsulphonyl radicals, Δ(C₂H₅, C₂H₅SO₂). The addition reaction of ethyl radicals with various molecules has been discussed and their reaction with oxygen shown to be much faster than their reaction with sulphur dioxide, the difference being much more marked than with methyl radicals.