Diels , Otto Paul Hermann

(1876–1954) German organic chemist

The son of Hermann Diels, a famous classical scholar, Diels was born in Hamburg, Germany. He gained his doctorate under Emil Fischer in Berlin (1899), becoming professor there in 1906. From 1916 until his retirement in 1948 he was professor at Kiel. In 1906 he made an extremely unexpected discovery, that of a new oxide of carbon, carbon suboxide (C₃O₂), which he prepared by dehydrating malonic acid with phosphorus pentachloride. Diels's second major discovery was a method of removing hydrogen from steroids by means of selenium. He used this method in research on cholesterol and bile acids, obtaining aromatic hydrocarbons that enabled the structures of the steroids to be deduced.

In 1928 Diels and his assistant Kurt Alder (1902–1958) discovered a synthetic reaction in which a diene (compound containing two double bonds) is added to a compound containing one double bond flanked by carbonyl or carboxyl groups to give a ring structure. The reaction proceeds in the mildest conditions, is of general application, and hence of great utility in synthesis. It has been used in the synthesis of natural products, such as sterols, vitamin K, and cantharides, and of synthetic polymers. For this discovery Diels and Alder were jointly awarded the Nobel Prize for chemistry in 1950.