The catalytic properties of aliphatic ketones to promote bleaching reactions of peroxymonosulfate with kraft softwood pulp was studied. The in-situ generation of substituted dioxiranes from keto compounds and peroxymonosulfate was demonstrated to be an effective bleaching technology. This bleaching system was shown to be very sensitive to the nature of the alkyl groups attached to the carbonyl group. Studies reported in this paper suggest that acetone may have the optimal structural features for catalyzing the bleaching properties of peroxymonosulfate.