Organic Chemists Contributing to Dyes and Colours
Background - Why is this important?
Textile dyes in a range of colours on a market stall
The rich diversity of colour which surrounds us plays an important part in our experience of everyday life, from the variety of colour found in the natural world to the myriad of hues and shades available through synthetic dyes and pigments.
What did the organic chemists do?
It is now a little over 150 years since British chemist, William Henry Perkin, serendipitously discovered the first synthetic dye, mauveine. He was initially carrying out research aimed at developing a synthetic route to quinine, the antimalarial drug. When Perkin was a chemist, analytical tools such as NMR, that organic chemists now use every day to determine what they have made, had not been discovered. Perkin would have only known that the components of quinine were carbon, nitrogen, oxygen and hydrogen using combustion analysis (burning the compound in air). Perkin treated an aromatic amine, aniline with an oxidising agent, potassium dichromate (K2Cr2O7). He hoped that the potassium dichromate would add oxygen to aniline, which contains carbon, nitrogen and hydrogen, to make quinine.
The reaction gave a black product from which Perkin was able to isolate a small amount of a bright purple compound. Perkin was a skilled chemist, but also an excellent entrepreneur, and realised the potential for the purple compound to be used as a dye.
It was named mauveine, and a factory was set up to produce it in large quantities. The beautiful purple materials that resulted were highly sought after, even by royalty! Queen Victoria famously wore a mauveine-dyed dress.
Today, there remains a need for new synthetic colourants with increasingly enhanced properties for diverse applications, such as laser dyes and dye-sensitised solar cells as well as for more traditional uses.
In addition, organic chemists must develop ever more efficient processes for their manufacture which reduce the environmental impact of the chemical industry.
The diketopyrrolopyrroles are an important class of red pigments, but the first example was only observed as a minor by-product obtained in low yield. A team of organic chemists at Ciba Geigy developed a simple, efficient and scalable method for the manufacture of this important class of compounds from readily-available starting materials. This route also allows access to analogues where changes in the symmetrical substituent on each side of the ring system are used to tune the optical properties of the pigment.
Synthesis of diketopyrrolopyrroles
What is the impact?
Organic synthesis has allowed us to develop a huge diversity of synthetic dyes and pigments to complement the colourful world that nature has provided.
As well as revolutionising fashion and creating the dye industry, this marked the foundation of the wider chemical industry as we know it today. In the UK, this has grown into a hugely important and valuable sector, making a contribution to GDP valued at £3.8bn in 2007 and supporting 69,000 jobs.
Also of interest
A fun way to find out more about the discovery of the synthetic dye mauveine
Find all our resources on Learn Chemistry
Stephen Batchelor really can help you achieve a ‘whiter wash’. With over 70 patents, he is one of Unilever’s top inventors. Manisha Lalloo discovers what inspires him
This book provides an up-to-date insight into the chemistry behind the colour of the dyes and pigments that make our world so colourful.
Contact and Further Information
Dr Anne Horan
Programme Manager, Life Sciences
Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge, CB4 0WF
Tel: 01223 432699