The diastereoselectivities in the self-photoinduced single oxygen and m-chloroperbenzoic acid oxidations of two series of sec-alkyl 4-nitrobenzenesulfenates to the corresponding 4-nitrobenzenesulfinates have been measured. The diastereoselectivities are only moderate but show some interesting trends with the nature and size of the functions in the arkyl group. Sulfonate formation also occurs, the extent of which increases with increasing size of the substituents in the alkyl group. The sulfonates are not formed by the further oxidation of the sulfinates. A mechanism for the formation of the sulfinates and sulfonates is proposed that involves the initial formation of a peroxysulfoxide intermediate which, when sterically unencumbered, can react with the starting sulfenate to generate two molecules of sulfinate but, when sterically encumbered, undergoes ring closure to form an alkoxythiadioxirane intermediate which can react with the starting sulfenate or undergo ring opening to produce the sulfonate. The effect of the incursion of other reactions on the relative yields of the sulfinates and sulfonates is also discussed.