Baeyer, Johann Friedrich Wilhelm Adolf von (1835–1917)

German organic chemist who synthesized the dye indigo in 1880. He discovered barbituric acid in 1863, later to become the parent substance of a major class of hypnotic drugs. In 1888 he carried out the first synthesis of a terpene. He was awarded the Nobel Prize for Chemistry in 1905 for his work in organic dyes and hydroaromatic compounds.

Baeyer was born in Berlin and studied there and at Heidelberg. He became professor of chemistry at the University of Strasbourg in 1872 and three years later at Munich, where he stayed for the rest of his career.

Baeyer discovered fluorescein in 1871. He also found the resinous condensation product of phenol and formaldehyde (methanal), which Leo Baekeland later developed into the first thermosetting plastic Bakelite.

His work with ring compounds and the highly unstable polyacetylenes led him to consider the effects of carbon–carbon bond angles on the stability of organic compounds. He concluded that the more a bond is deformed away from the ideal tetrahedral angle, the more unstable it is; this is known as Baeyer's strain theory. It explains why rings with five or six atoms are much more common, and stable, than those with fewer or more atoms.