X-Ray and neutron powder diffraction studies of the crystal structure of vitamin K3

Abstract

The previously unknown structure of vitamin K₃ (menadione, 2-methyl-1,4-naphthoquinone, C₁₁H₈O₂), a synthetic compound from which it is possible to derive the naturally occurring K vitamins, has been solved from X-ray powder diffraction data. Solution was achieved using simulated annealing and restrained Rietveld refinement, using restraints derived from similar known structures. Further refinement has been carried out using neutron diffraction data; this confirmed the molecular packing and allowed further insight into the structural detail with regard to methyl group orientation, thus allowing the proposal of an extensive C–H⋯O hydrogen bonding scheme by reference to comparable known structures. The crystal structure consists of chains of molecules lying head-to-tail. This study may aid the understanding of the biological activity of vitamin K.