X-ray and neutron diffraction studies of the crystal and molecular structure of the predominant monocarboxylic acid obtained by mild acid hydrolysis of cyanocobalamin. Part I. X-ray diffraction studies of airdried crystals

The crystal structure of air-dried crystals of the O-monocarboxylic acid of cyanocobalamin, E2, has been solved by x-ray analysis. The lattice constants area =14-51 A,b = 1709 A,c = 16.35A, β = 103°; space group P2₁. Phase angles were derived from observations on anomalous dispersion effects for 2567 of the measured 2875 pairs of reflections,hkl andhkl, and used in the solution of the structure. The intensities of reflexions were eye estimated from Weissenberg photographs. The molecular arrangement is very different from that of other cyanocobalamins; the corrin rings of neighbouring molecules are atca 90° to one another. It was not possible to recognise the one acid group among the amides with certainty.