Johann Friedrich Wilhelm Adolf von Baeyer was born in 1835, in Berlin. He began his undergraduate studies at the University of Berlin between 1853 and 1855. After initially showing an interest in physics and mathematics, Baeyer began to concentrate on chemistry and eventually moved to work in Bunsen's laboratory in Heidelberg.
The Chemistry of Ethyl Chloride and Cacodyl
Studies on a compound called ethyl chloride produced Baeyer’s first published work in 1857. Once widely used to make tetraethyl lead as an anti knock agent in petrol, ethyl chloride is now mainly utilised in the manufacture of ethyl cellulose in paints and cosmetics. In 1858 Baeyer worked with Kekulé in Heidelberg, before receiving his doctorate from Berlin University for his work on cacodyl compounds.
Cacodyl and its derivatives are known as “organometallic” substances as they contain one or more metals bonded to carbon containing groups. Cacodyl itself is a poisonous oily liquid with a garlicky odour which undergoes spontaneous combustion in dry air! Cacodyl was considered for use as a poisonous gas weapon in WW1 but ultimately it never reached the battlefield.
The Discovery of Barbituric Acid
Baeyer qualified as a university teacher in 1860, following his discovery of barbituric acid which is the parent compound of the barbiturate family of chemicals. Barbiturates are now very well known as illegal drugs but they also have extensive pharmaceutical applications. Baeyer made the discovery on 4. December 1864 which is the feast of St Barbara and hence the name given to this new compound.
The Synthesis of Indigo Dye
After becoming a lecturer in organic chemistry at the Berlin Trade Academy, Baeyer began the work on indigo dye that was to bring him widespread acclaim and ultimately, along with his other outstanding discoveries, the Nobel Prize. Known since ancient times and originally made from snails or plants like woad, indigo dye could only be made on a relatively small scale until Baeyer’s discoveries led to its industrial production.
Baeyer first made indigo in 1878 and a second, more successful, synthesis followed two years later using nitrobenzaldehyde and acetone reacting in alkaline conditions. Baeyer announced the chemical structure of indigo three years later. The German chemical giant BASF developed a manufacturing process that was in use by 1897, and by 1913 natural indigo had been almost entirely replaced by the synthetic product. Nowadays, indigo is manufactured on an enormous scale, not least for the dying of jeans.
The Development of Phthalein Dyes
Baeyer also made an enormous contribution to our understanding of the chemistry of the so called phthalein dyes. For example in 1871 at the newly established Strasburg University, Professor Baeyer synthesed both phenolphthalein and fluorescein dyes artificially. A young Hermann Fischer was greatly influenced by Baeyer’s research methodologies at Strasburg.
Phenolphthalein is now extensively used as a pH indicator in titrations and also to test blood in the Kastle-Meyer test. Its historical use as a powerful laxative has now diminished because of phenolphthalein’s carcinogenic properties. Fluorescein is widely used in ophthalmology, forensic science and as a tracer dye in environmental chemistry.
In 1881 the Royal Society of London awarded Baeyer the Davy Medal for his work with indigo. In 1905 he was awarded the Nobel Prize in Chemistry "in recognition of his services in the advancement of organic chemistry and the chemical industry, through his work on organic dyes and hydroaromatic compounds". Baeyer died on August 20th 1917 at the grand old age of 82.
 |
