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, C16H16N2O 4 .H2O, has an extensively hydrogen-bonded crystal structure involving N-H ... O(hydroxy), (hydroxy)O-H ... O(water) and (water)O-H ... O(carbonyl) in teractions in a three-dimensional network, with both the oxidation product and the water molecule lying on a twofold axis. The two halves of the molec ule have essentially the same geometry as paracetamol in its two known anhy drous polymorphs, except for the variation observed in the dihedral angle b etween the aromatic ring and its amide substituent.