Crystal and molecular structure of acetazolamide (5-acetamido-1,3,4-thiadiazole-2-sulphonamide), a potent inhibitor of carbonic anhydrase

Crystals of the title compound, a potent inhibitor of carbonic anhydrase, are colourless, triclinic, with unit-cell dimensions, a= 5·318(4), b= 9·065(4), c= 9·430(7)Å, α= 105·44(2), β= 98·59(2), γ= 100·42(2)°, Z= 2. The structures was solved by the heavy-atom method and refined by least-squares techniques to a final R of 0·028 for 1054 observed reflections. The distances and angles are compared with those in other sulphonamides of varying biological activity. The mechanism of inhibition of carbonic anhydrase is discussed.