Organic Chemistry Contributing to Flavours and Fragrances

Everyday products such as shampoos, cleaning products and deodorants all contain fragrances and perfumes. Developing these fragrances is the work of organic chemists, who craft complex mixtures of organic molecules to achieve the desired scents.

The fragrance and flavour industry, dominated by 6 large international companies, was estimated to be worth around $22 billion in 2010. So getting perfumes right is big business, and the study of fragrances involves a lot of complex chemistry. Researchers will perform studies on perfume ingredients to determine the relationship between molecular structure and function, in the same way that drug discovery chemists will.

For example, chemists can understand the effect of moving just one functional group. The two structures below are nerol and muguet. Nerol has a rosy smell, while muguet is the familar lily of the valley fragrance. The only difference between the structures is the positioning of the methyl group, yet the impact on the fragrance is great.

Hedione

Organic chemistry has also helped to produce perfume ingredients more efficiently. One of the most common fragrance additives is hedione, a molecule which was first isolated from jasmine oil. It helps to blend, fix and enhance the scent of other components in perfumes, so it is added to nearly all man-made fragrances.

However, hedione has two naturally occurring isomers, which differ depending on the arrangement of the two side chains. The substituents can either be on the same side of the ring or on opposite sides. Only the (+)-(cis) form, when the substituents are on the same side, is active as a perfume additive.

Until 1989, there was no method to convert between these two isomers, so a mixture which was mainly the other (trans) isomer had to be used. However, in 1989 Nippon-Zeon developed a process to convert the trans-form in the cis-form.

This original process only gave around a 10% yield of the cis-form, but improvements through the 1990s eventually led to an effective route to high yields of the desirable compound. This used an organometallic catalyst in an asymmetric hydrogenation, to control where the substituents were added.

Since then, more efficient routes to hedione have also been developed, helping to provide high volumes of this very important perfume additive.

Also of Interest

The sweet scent of success

Emma Davies pokes her nose into some of the world’s most celebrated perfume molecules.

Who's who: Studying fragrances

Sarah Houlton tries to entice us into a career in the flavourings and fragrances industry.

Profile: Sense of success

‘I enjoy a challenge’, Nathan Lawrence, senior research scientist at Schlumberger Research, tells Emma Davies.

Advances in Flavours and Fragrances

Copyright: 2007
Karl A D Swift
The chemistry of flavours and fragrances is of great interest to academics and industrialists alike and this book presents the most recent research in this key area

The Chemistry of Fragrances

Copyright: 2007
David Pybus
This unique book gives an insider view of ""mixing molecules"" from behind the portals of modern-day alchemy. It will be enjoyed by chemists and marketeers at all levels.