The reaction of phenol with hypochlorite in strongly alkaline solution gives variable yields of 3,5,5-trichloro-1,4-dihydroxycyclopent-2- enecarboxylic acid, which on treatment with 36N sulphuric acid produces 3,5-dichloro-2-hydroxy-4-oxocyclopent-2-enecarboxylic acid. Dry distillation of this product under reduced pressure gives the mono-en01 of 2,4-dichlorocyclopentane-1,3-dione. The nature of these reactions is discussed.