Thursday, March 22, 2012

What's wrong with this diagram?

Take a look at the following image:

Source: NCBI PubChem database
I'm relatively certain there's something wrong here. Can you guess where the problem is? Answer after the jump.

Take a close look at the two ferrocyanide ligands on the right. Do you see it now? An observant viewer might notice that the structure contains a bit of an impossibility:

Carbon can only carry 4 bonds. In this case (if you count the coordinating bond) this carbon contains 7 bonds. Carbon doesn't have enough valence electrons to do that. If you look at the PubChem entry for this compound (Ferric Ferrocyanide, also known as Prussian Blue), you will see that the molecular formula is C18Fe7N18 , which doesn't agree with the diagram. Now, before you go on saying, "How can a government-run database have such an egregious error,  why are they wasting my tax dollars by publishing bad information!", observe that PubChem gets its data from numerous sources, wherever this structural diagram was sourced from, it had the error in it already. Hopefully they will fix it at some point, but it serves as an example of why you should always be cautious of any information supplied, and always look at multiple sources when possible. Those 3 ligands should be the same:

Pleas note that while I'm certain that this is what was meant, I have no idea if the compound is actually arranged this way structurally. I'm a relatively serious amateur scientist, but that's just it; pay special attention to the amateur part.

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