File talk:Cyanocobalamin-3D-sticks.png

Grave errors in structure Cyanocobalamin-3D-sticks.png

This 2008 structure must NOT be used to represent cyanocobalamin (vitamin B12), as it contains several grave errors, particularly in the central chromophore, which is NOT a corrin at all: only ring B (top left) is a pyrroline ring (but with the position of its propionic side chain above instead below, and the acetic acid side chain shows a C-O instead a C=O group); "rings" C (top right), D (lower right), and A (lower left) are not 5-membered rings, each missing a bond; the configurations (up/down) of the side chain in "ring C", and of both methyl groups as well as the acetic acid side chain in "ring A" are all wrong; the Co-CN group is linear, not with an angle as shown.

A second, older and differently oriented structure in this Commons entry shows all the hydrogens ("17:46, 1 August 2006"). This, however, leads to so much overlap and clutter that I can only say that this structure does contain four pyrrolenine rings, but I am not able to ascertain the correctness of the structure much beyond that.

I created a new Wikimedia Commons entry Vitamin_B12_hydrate.png, based on an x-ray crystal structure analysis by Dorothy Hodgkin et al. (1964); this may be used as replacement structure (as it already is in the article wikipedia:Vitamin B12 total synthesis), or FileːVitamin B12 - cyanocobalamine.jpg.

Easyloc (talk) 11:35, 9 January 2021 (UTC)

Just a note for the record book: I've created File:Cyanocobalamin-from-xtal-3D-st-noH.png, File:Cyanocobalamin-from-xtal-3D-bs-17.png, and File:Cyanocobalamin-from-xtal-Co-coordination-3D-bs-17.png to address these problems. Thanks for pointing them out, Easyloc. --Ben (talk) 16:48, 30 January 2021 (UTC)