Twinning by merohedry in cyclohexanone oxime: a revised structure.

The crystal structure of cyclohexanone oxime, C(6)H(11)NO, 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, 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.