Connectivity Rules !

So with my pupils having just finished their final organic paper I decided to base this post around connectivity – the attachment of atoms in a molecule. I introduce its importance in class by showing this brilliant video by Professor Dave which he made after spotting a poor structural representation of a molecule in the opening credits of Brian Cox’s tv programme. This video emphasises the importance of correct representations and after that I show no mercy and the red pen is out ready to start circling ! Mark schemes also see connectivity as an important chemical skill and you can see that when drawing an alcohol the examiners will penalise if the connectivity of the carbon to oxygen is not shown correctly.

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Only last week I read a post by the eminent chemistry blogger Derek Lowe about a structure he spotted in a paper about piperazines.  Now, although the connectivity is correct he points out the poor bond lengths and angles. Even more disappointing they do not show the stereochemistry of the hydroxy groups and that could mean the diagram could represent up to 8 different structures. I would like to think by the time our A level students sit their final organic paper they understand the importance of correct representation and if a career in chemistry beckons they would not let mistakes like this occur.

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So outside of chemistry who really cares? Well this is a true story. Recently I was in a very trendy coffee shop with the organic chemist (check out his guest post for me here) who noticed that the barista had tattoos of the structures of caffeine and theobromine (chocolate). When the organic chemist mentioned the tattoos the barista became quiet and sullen. Turns out she thought he had spotted the mistake on the structure of caffeine, a methyl group CH3 was incorrectly tattooed as OH3. A permanent reminder that there is no room for mistakes with your structural representations.

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