List, MacMillan win 2021 Nobel Prize in Chemistry for development of asymmetric organocatalysis
The Royal Swedish Academy of Sciences has awarded the Nobel Prize in Chemistry 2021 for the development of asymmetric organocatalysis to:Background on the Award
The rapid expansion in the use of organic catalysts is primarily due to their ability to drive asymmetric catalysis. When molecules are being built, situations often occur where two different molecules can form, which – just like our hands – are each other’s mirror image. Chemists will often only want one of these, particularly when producing pharmaceuticals.
Many molecules exist in two variants, where one is the mirror image of the other. These often have completely different effects in the body. For example, one version of the limonene molecule has a lemon scent, while its mirror image smells like orange.
Catalysts are thus fundamental tools for chemists, but researchers long believed that there were, in principle, just two types of catalysts available: metals and enzymes. Benjamin List and David MacMillan are awarded the Nobel Prize in Chemistry 2021 because in 2000 they, independent of each other, developed a third type of catalysis. It is called asymmetric organocatalysis and builds upon small organic molecules.
Organocatalysis has developed at an astounding speed since 2000. Benjamin List and David MacMillan remain leaders in the field, and have shown that organic catalysts can be used to drive multitudes of chemical reactions. Using these reactions, researchers can now more efficiently construct anything from new pharmaceuticals to molecules that can capture light in solar cells.
Organic catalysts have a stable framework of carbon atoms, to which more active chemical groups can attach. These often contain common elements such as oxygen, nitrogen, sulphur or phosphorus. This means that these catalysts are both environmentally friendly and cheap to produce.
Reaction from the Committee
A Deeper Dive into the discoveries, from the Nobel Prize committee
Chemists can create new molecules by linking together small chemical building blocks, but controlling invisible substances so they bond in the desired way is difficult. Benjamin List and David MacMillan are awarded the Nobel Prize in Chemistry 2021 for their development of a new and ingenious tool for molecule building: organocatalysis. Its uses include research into new pharmaceuticals and it has also helped make chemistry greener.
Catalysts accelerate chemical reactions
In the nineteenth century, when chemists began exploring the ways that different chemicals react with each other, they made some strange discoveries. For example, if they put silver in a beaker with hydrogen peroxide (H2O2), the hydrogen peroxide suddenly began to break down into water (H2O) and oxygen (O2). But the silver – which started the process – did not seem affected by the reaction at all. Similarly, a substance obtained from sprouting grains could break down starch into glucose.
In 1835, the renowned Swedish chemist Jacob Berzelius started to see a pattern in this. In the Royal Swedish Academy of Sciences’ annual report, describing the latest progress in physics and chemistry, he writes about a new “force” that can “generate chemical activity”. He listed several examples in which just the presence of a substance started a chemical reaction, stating how this phenomenon appeared to be considerably more common than was previously thought. He believed that the substance had a catalytic force and called the phenomenon itself catalysis.
Catalysts produce plastic, perfume and flavoursome food
A great deal of water has run through chemists’ pipettes since Berzelius’ time. They have discovered a multitude of catalysts that can break down molecules or join them together. Thanks to these, they can now carve out the thousands of different substances we use in our everyday lives, such as phar- maceuticals, plastics, perfumes and food flavourings. The fact is, it is estimated that 35 per cent of the world’s total GDP in some way involves chemical catalysis.
In principle, all catalysts discovered before the year 2000 belonged to one of two groups: they were either metals or enzymes. Metals are often excellent catalysts because they have a special ability
to temporarily accommodate electrons or to provide them to other molecules during a chemical process. This helps loosen the bonds between the atoms in a molecule, so bonds that are otherwise strong can be broken and new ones can form.
However, one problem with some metal catalysts is that they are very sensitive to oxygen and water so, for these to work, they need an environment free of oxygen and moisture. This is difficult to achieve in large-scale industries. Also, many metal catalysts are heavy metals, which can be harmful to the environment.
Life’s catalysts work with astounding precision
The second form of catalyst is comprised of the proteins known as enzymes. All living things have thousands of different enzymes that drive the chemical reactions necessary for life. Many enzymes are specialists in asymmetric catalysis and, in principle, always form one mirror image out of the two that are possible. They also work side by side; when one enzyme is finished with a reaction, another one takes over. In this way, they can build complicated molecules with amazing precision, such as cholesterol, chlorophyll or the toxin called strychnine, which is one of the most complex molecules we know of.
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