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Diels, Otto (Paul Hermann)

hydrocarbon diels’s skeleton dioxide

[deels] (1876–1954) German organic chemist: co-discoverer of Diels–Alder reaction.

A member of an academically talented family, Diels studied chemistry in Berlin with . Most of his life was spent in the University of Kiel. In 1906 he discovered a new oxide of carbon (the monoxide and dioxide were long known); he made tricarbon dioxide (C3O2 ) by dehydrating malonic acid with P2O5 :

He showed in 1927 that cholesterol is dehydrogenated by heating with selenium and that the hydrocarbon products include one of melting point 127°C, now known as Diels’s hydrocarbon. The method can be applied generally to steroids, and many yield Diels’s hydrocarbon; in this way and by interconversions this biologically important steroid group was shown to all have the same carbon skeleton. By 1934 Diels’s hydrocarbon had been synthesized by others and its structure was the critical clue that allowed other steroid structures to be assigned, all containing the four-ring skeleton of Diels’s hydrocarbon: this skeleton became the defining feature of steroids.

In 1928, with his assistant K Alder (1902–58), Diels discovered the valuable general synthesis now known as the Diels–Alder reaction. In this, a conjugated diene reacts by 1,4-addition with one of a large group of unsaturated compounds (dienophiles) to give, usually, a six-membered ring compound as the product. The method has proved of great value in the synthesis of complex organic compounds. Diels and Alder shared a Nobel Prize in 1950.

Diesel, Rudolph (Christian Karl) [next]

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