In ozone reactions, singlet dioxygen [O2 (1Δg)] is formed when ozone reacts by O-atom transfer. O2 (1Δg) yields were determined for more than 50 compounds using as reference the reaction of hydrogen peroxide with hypochlorite. Close to 100% yields were found in the reaction of O3 with sulfides, disulfides, methanesulfinic acid, and nitrite. In accordance with this, the only products are: methionine sulfoxide, methanesulfonic acid, and nitrate for the ...