2006 WINNER

By Phillip Broadwith
University of Cambridge

Winner of the 20-28 category

'You might get an anti-cancer drug or a useless blob of gunk'

Chemistry is often considered an arcane, mysterious science practised by wild-haired boffins hiding away in laboratories with only beakers of brightly coloured, smoking solutions for company. In reality i's not even as exciting as that - the solutions are mostly colourless, and if they start smoking it's usually time to run away.

It gets interesting when you consider what's actually going on inside the flask, where molecules are being built up from atoms in the world's smallest Meccano set. And if you can find a better way of joining together the Meccano, maybe you could win a Nobel Prize - as Yves Chauvin, Richard Schrock and Robert Grubbs did when they became the latest crop of chemistry laureates.

The ability to build molecules with particular shapes is one of the keys to synthetic organic chemistry, because it is largely the overall shape of a molecule that dictates whether it is an anti-cancer drug, a fabric dye, a food preservative or a useless blob of gunk.

To be able to bolt together molecules of different shapes, chemists take simple building blocks and use chemical reactions to make new molecules. An example of this would be the oxidation of the alcohol in wine to vinegar, a process that may take days or weeks in an open bottle of burgundy but can be achieved rapidly in a laboratory under significantly more control.

Chauvin, Schrock and Grubbs won their Nobel Prize for harnessing the power of the alkene metathesis reaction. An alkene can be considered as a pair of carbon atoms, holding onto each other with both hands, with the rest of the molecule attached to their backs. They are crucial in the building of more complex molecules. Metathesis is a powerful way of joining molecules together, making a useful alkene bond in the process.

It was Chauvin who, in 1971, finally shed some light on these reactions. His experiments revealed the nature of what has been described as a "partner-changing dance" of molecules. This dance is led by a metal catalyst molecule, partnered with one of the molecules to be joined. As this couple whirl and tumble around the dance floor of the reaction flask, they encounter other couples (the alkene portions of other molecules). At this point both molecules open their double-handed hold and briefly join together in a type of square-dance before changing partners and parting company; the catalyst takes its new partner to pick up another lonely couple, leaving the newly joined product partnership to dance the night away.

With this new understanding of the partner-changing process, it was possible to design much more effective catalysts. The catalyst is the key to the whole process - as the leader of the dance it can choose with whom it dances: some alkenes are better dancers (like people), so these are favoured by the catalyst, allowing the chemist to control the outcome of the reaction.

Standing on the shoulders of the quietly spoken Frenchman, both Schrock and Grubbs have invented catalysts that are reactive enough to bring together a wide variety of alkenes but discerning enough partners to avoid tearing apart delicate molecules during the dance. The competition between these two Americans and their business sense made their inventions available to the everyday organic chemist, allowing them to find application in all branches of the chemical industry.

Current applications of metathesis include manufacture of plastics with tuneable properties for baseball bats and lightweight bullet-proof materials, along with agricultural pheromones. Pheromones are molecules that some insects use to communicate and were extremely costly and wasteful to produce by previous methods. With metathesis it is possible to combine by-products of the oil industry with natural plant oils to make them quickly and cheaply, with few waste products. They can be used as an environmentally friendly way of dealing with insect pests such as the mosquitoes that spread West Nile Virus.

These, along with wide-ranging uses in the pharmaceutical and petrochemical industries, make metathesis one of the most powerful tools available to the modern synthetic chemist.

We'd better hope that the boffins keep beavering away in their laboratories, quietly building structures that even they can never see, but shape the world in which we live.

Phillip Broadwith, 25, is a doctoral student studying synthetic organic chemistry at Cambridge University. He is trying to make a molecule that is naturally produced by an alga from the Philippines to end a scientific dispute about its shape and because it is thought to have anticancer and anti-bacterial properties. On being told he had won the older category, he shrieked: "You are joking!"