(b. Könighsuü Germany [now Chorźow Poland], 10 July 1902 d. Cologne, Germany, 20 June 1958)
Alder, the son of Schoolteacher in heavily industrialized area around Kattowitz (now Katowice) in Upper Silesia, received his early education in the German schools of Königshütte. When the region became a part of the new polish nation after the end of World War I, his family left in order to remain in Germany. After completing on Oberrealschule in Berlin, Alder studied chemistry at the University of Berlin and later at the University of Kiel, where he received the doctorate in 1926. His dissertation, “On the Causes of the Azoester Reaction,” was carried out under the direction of Otto Diels. Alder continued his work at Kiel, being made a reader in organic chemistry in 1930 and extraordinary professor of chemistry in 1934. He became a research director at the Bayer Werker in Leverkusen, a branch of I.G. Farbenindustrie, in 1936. In 1940 he returned to academic life as ordinary professor of chemistry and director of the chemical institute at the University of Cologne, where he served until his death. In 1949-1950 he was dean of the Faculty of Philosophy. With Diels, he received the Nobel Prize for chemistry in 1950.
Alder’s principal contributions to organic chemistry are associated with the diene synthesis, which grew out of his studies in Diels’s laboratory and was first reported in 1928. The synthetic method, frequently referred to as the Diels-Alder reaction, involves the addition of dienes (compounds with conjugated unsaturation, i.e., double bonds on adjacent carbon atoms) to dienophiles (compounds having a double bond activated by nearby carbonyl or carboxyl groups). A simple example is the addition of butadient to maleic anhydride.
Although a few reactions of this type had been reported over a period of more than 30 years, Diels and Alder recoginzed the widespread and general nature of the reaction and subsequently spent much of their lives in developing the consequences. They called particular attention to the ease with which such reactions take place and the high yield of adduct.
Their earlier work involved the addition of cyclo pentadient (I) to a p-quinone (II). The nature of the product (III) of this reaction was the subject of controversy from the time of its preparation by Walter Albrecht in 1893. Diels and Alder, utilizing the corresponding addition of Cyclo pentadient to azoester
(IV), were able to identify the structure of Albrecht’s compound correctly.
(It will be recalled that azoester had been the subject of Alder’s doctoral dissertation.) The two investigators were able to show that, besides azoester and p-quinone, they could obtain a reaction of cyclopentadiene with the double bonds in maleic, citraconic, and itaconic acids. They also demonstrated that the adduct is always a six-membered ring, with the addition taking place between the double bond of the dienophile and the carbon atoms at the 1 and 4 positions in the diene.
At first in association with Diels, and then independently with his own students, Alder studied the general experimental conditions of the diene synthesis and the overall scope of the method for synthetic purposes. He was a particularly able stereochemist and showed that diene addition took place at double bonds with a cis configuration. In his Nobel prize adderss he listen more than a dozen diene types of widely differing structures that had been shown to participate in the reaction. Similarly, he showed that the reaction was equally general with respect to dienophiles, provided the double bond was properly activated by nearby carbonyl, carboxyl, cyano, or nitro groups. Unsaturated compounds without such properly placed activating groups failed to participate in an addition reaction. Many of the compounds studied were prepared in Alder’s laboratory for the first time. The Diels-Alder reaction also became useful in structural studies because it provided an analytical means for the detection of conjugate double bonds.
The bridged-ring compounds formed by the use of cyclic dines were closely related to such naturally occurring terrenes as camphor and norcamphor. The diene synthesis stimulated the understanding of terpene chemistry by providing a synthetic method for preparing such compounds. The ease with which such reactions took place suggested that the diene synthesis might occur in biosynthetic reactions in nature. This role in biosynthesis was also found relevant in connection with anthraquinone-type dyes and a compound that could substitute for vitamin K in stimulating blood coagulation.
The diene synthesis proved to have broad applicability, not only in laboratory syntheses but in commercial operations as well. Commercial products prepared by Diels-Alder reactions include dyes, drugs, insecticides (e.g. dieldrin, aldrin, chlordane), lubricating oils, drying oils, synthetic rubber, and plastics.
During his period of industrial research Alder was involved in the study of polymerization processes connected with the production of Buna-type synthetic rubbers by polymerization of butadiene with such suitable compounds as styrene.
In 1955 he joined seventeen other Nobel laureates in issuing a declaration requesting the nations of the world no renounce war.
1. Original Works Most of Alder papers were published Berichte der deutschen chemischen Gesellschaft, Liebig’s Annalen der chemie, and Angewandte Chemie. For a full bibliography, see Poggendorff. The orginal paper on the diene synthesis is in Liebig’s Annalen der chemie, 460 (1928), 98-22. Alder’s Nobel Prize address, “Dien synthese und verwandte Reaktionstypen,” appears in Les prix nobel in 1950 (Stockholm, 1951), pp. 157-194. An English translation is available in the Nobel Foundation’s Nobel Lectures Including Presentation Speeches and Laurecttes’ Biographies, Chemistry, 1942–1962 (Amsterdam, 1964), pp.266-303. His two main works ate “Die Methoden der Diensynthese,” in Handbuch der biologichen Arbeits methoden, sec. II, pt. 2 (1933); and Neuere Methoden der präparativen organischen Chemie (berlin, 1944).
II Secondary Literature. There is no lengthy biography of Alder. Short Sketches are Eduard Farber, Nobel Prize Winners in Chemistry (New York, 1953), pp.205-207; M. Günzl-Schumacher, in Chemikerzeitung, 82 (1958), 489-490; H. Hauptman, in Boletim da Associaçāo quimica do Brasil, 9 (1951), 1-6; M. Lora-Tamayo, in Revista de ciencia aplicada (Madrid), 14 (1960), 193-205; McGraw Hill Encyclopedia of Science and Technology (New York, 1966), I, 6-7; Lex Prix Nobel in 1950 (Stockholm, 1951), pp. 117-118; and Nobel Lectures Including Presentation Speeches and Laureates’ Biographies, Chemistry, 1942–1962 (Amsterdam 1964), pp.304–309.
Aaron J. Ihde