The reacticins of perfluorocyclopent-2-en-1-one and perfluorocyclobutenone with various nucleophiles have been studied. The enones are attacked by nucleophiles at C-3 via an addition-elimination sequence to afford the 3-substituted perfluorinated enones. Multiple addition products were isolated when the enones were treated with mercaptans. Perfluorocyclopent-2-en-1-one reacted with potassium acetate to give, after hydrolysis, 3- ...