Dr David Fox: Aromaticity; going round in circles

Dr David Fox: Aromaticity; going round in circles

On Thursday 22nd November, the College’s Chemistry department was lucky to be visited by Dr David Fox from the School of Chemistry at the University of Warwick.  David studied undergraduate chemistry at Wadham College, Oxford, then after his PhD, he moved to a research job at the Department of Chemistry and Medicine at Cambridge before joining Warwick University where he lectures and works as a consultant chemist for RxCelerate, a drug discovery company.

David spent time during the day inspiring the pupils who he spoke to in several lessons – a Lower Sixth IB class that was learning how to calculate formal charge; an Upper Sixth A level set getting to grips with organic synthesis and Upper Sixth IB pupils that were analysing the samples of aspirin that they had synthesized in the laboratory.

In the evening, he gave a lecture entitled ‘Aromaticity; going round in circles’. He started by dispelling the myth that Kekule was the person who discovered benzene and informed us that it was actually Michael Faraday who distilled benzene from whale oil (which was commonly used for lighting) in 1825 and at that time he named it bi-carburet of hydrogen because they thought that the empirical formula was C2H.

The first person to draw a representation of benzene was Loschmidt in 1861 who represented the benzene structure as a simple circle.  It wasn’t until 1865 that Kekule proposed a structure for benzene which he subsequently revised several times before coming to the well-known Kekule structure of the alternating double and single bonded carbons arranged in a hexagon. The problem with this was that the structure meant that there should be isomers of substituted benzenes that in reality did not exist. So, Dr Fox set about arguing which of the structures shown below best represents benzene.

It was many years later in 1929 that Kathleen Lonsdale published the first X-ray crystallography images of derivatives of benzene showing a regular hexagon. This discovery meant that the carbon atoms were all equal distances apart. Soon after, Huckel used quantum mechanics to explain how overlapping p-orbitals form a delocalised -system around the whole hexagon. After further explanations of Huckel’s ‘4n+2 theory’, Dr Fox then gave examples of the applications of aromatic compounds (like benzene) in real life.  He explained how glow sticks work and why they have different colours. He also highlighted the fact that Kevlar (commonly used in bullet-proof jackets by police forces) and Nomex (used as a flame retardant) are isomers of each other; astonishing that a different spatial arrangement of the atoms causes such different properties in a compound.

He also told us the story of ‘Olympicene’, the molecule that he and fellow researchers ‘dreamed-up’ in 2010 as a way of representing the Olympic rings for the London 2012 games. They set to work and by 2012 they had a non-contact atomic force microscopy image of Olympicene - just in time for the 2012 London Olympic games.

This was a superb lecture which inspired the pupils to challenge the theories that they learn and move forward with their studies with an open mind and a desire to move research forward, make new compounds with important uses but also (as in the case of Olympicene) for the sake of art!

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