Twinning by merohedry in cyclohexanone oxime: a revised structure

The crystal structure of cyclohexanone oxime, C6H11NO, was reported as severely disordered in the trigonal non-centrosymmetric space group P3 [Olivato, Ribeiro, Zukerman-Schpector & Bombieri (2001). Acta Cryst. B57, 705-713]. Re-investigation of the crystal structure as twinned by merohedry in the trigonal centrosymmetric space group P (3) over bar, with a twofold rotation about [001] as twin law, resulted in a well ordered structure and low R values. The asymmetric unit contains three independent molecules, existing as a hydrogen-bonded trimer, having an R-3(3)(9) graph set.