An oxidatively coupled dimer of paracetamol

The title compound, 5,5'-bis (acetylamino) -2, 2'-di-hydroxybiphenyl, is a minor oxidation product formed from paracetamol. Its monohydrate, C16H16N2O4 .H2O, has an extensively hydrogen-bonded crystal structure involving N-H ... O(hydroxy), (hydroxy)O-H ... O(water) and (water)O-H ... O(carbonyl) interactions in a three-dimensional network, with both the oxidation product and the water molecule lying on a twofold axis. The two halves of the molecule have essentially the same geometry as paracetamol in its two known anhydrous polymorphs, except for the variation observed in the dihedral angle between the aromatic ring and its amide substituent.