Curtius, Theodor

(b. Duisburg, Germany, 27 May 1857; d. Heidelberg, Germany, 8 February 1928)

chemistry.

Most of curtius’ research was on nitrogen-containing organic substances, and two reactions he discovered were named for him: the conversion of an acid into an amine or an aldehyde and the conversion of an azide into an isocyanate.

Curtius was born into a scholarly family originally from Bremen. His grandfather, Friedrich Wilhelm Curtius was engaged in the manufacture of inorganic chemicals. After graduating from the Gymnasium at Duisburg Leipzig and served in the army from 1877 to 1878, becoming a first lieutenant. He studied in Heidelberg under Bunsen and under Kolbe’s direction at Leipzig wrote his doctoral dissertation, “Uber einige neue der Hippursäure analog konstituierte, synthetisch dargestellte Amidosäuren,” receiving the degree on 27 July 1882. Curtius worked in Baeyer’s laboratories in Munich from 1882 to 1886, when he went to the University of Erlangen as assistant and director of the analytical section of the chemical laboratories. In 1889 he declined an American offer (Worcester Polytechnic) to go to Kiel as professor of chemistry and director of the chemical institute. He succeeded Kekulé at Bonn in 1897 and Victor Meyer (who had succeeded Bunsen in 1889) at Heidelberg in 1898. There he was director of the chemical institute for twenty-eight years and was editor of the Journal für praktische Chemie. Curtius entertained himself and his friends by playing the piano, singing, and composing; and he shared his brother’s enthusiasm for mountain climbing.

Acting on Kolbe’s adevice, Curtius investigated the synthesis of hippuric acid by the method of Dessaignes, who had prepared the acid from the zinc salt of glycine and benzoyl chloride in 1853. Curtius improved the method, reporting the results in his doctoral dissertation. Baeyer suggested that he use the ethyl ester of glycine; and when Curtius treated it with sodium nitrite and hydrochloric acid, he discovered the first known aliphatic diazo compound, diazoacetic ester. In 1887 he treated the ethyl diazoacetate with concentrated sodium hydroxide, added hot dilute acid to the product, and discovered hydrazine. The commercial process developed by Friedrich Raschig in 1908(the oxidation of aqueous ammonia by sodium hypochlorite in the presence of gelatin) was used in Germany during World War II for the production of hydrazine to use in rocket fuel. In 1890 Curtius discovered hydrazoic acid HN₃, which he called “Stickstoffwasserstoffsäure” (azoimide), by treating benzoyl and hippuryl derivatives of hydrazine with nitrous acid. He reported in 1893 that hydrazoic acid is produced by the action of red fuming nitric acid on a dilute, ice-cold solution of hydrazine. Curtius believed that the structure of hydrazoic acid consisted of a hydrogen atom bonded to one nitrogen atom of a three-nitrogen-atom ring, in line with Emil Fischer’s proposed azide structure of 1878. Thiele pointed out in 1911 that a linear structure gives a better explanation of certain reactions, and a linear structure is accepted today.

In 1882 Curtius began a long series of researches into those compounds that Fischer named polypeptides in 1906. Using diazo compounds as intermediates, Curtius synthesized benzoyl derivatives of amino acids; and in 1904 he succeeded in synthesizing a hexapeptide, benzoyl pentaglycine-aminoacetic acid, by fusing ethyl hippurate with glycine. He investigated the rearrangement of aliphatic ketazines and aldazines into pyrazoline derivatives, prepared azides and hydrazides of acids, and obtained benzyl hydrazine from the reduction of benzaldazine. In 1894 Curtius discovered the first of two reactions that were later named for him, the conversion of an acid into the corresponding amine by way of the azide and urethane. By varying the technique, he was able to prepare the corresponding aldehyde in place of the amine in 1906. The second reaction bearing his name is the conversion of an azide into isocyanate, discovered in 1913.

Collaborating with Hartwig Franzen, Curtius began investigating plant chemistry in 1912. They found hexenal but no formaldehyde in green plants. The results of this work caused the abandonment of Baeyer’s hypothesis that hexoses are built up from the condensation of hydrated formaldehyde within the plant tissues.

BIBLIOGRAPHY

I Original Works. Curtius’ doctoral dissertation, Über einige neue der Hippusäure analog konstituierte, synthetisch dargestellte Amidosäuren, was published at Leipzig in 1882. Diazoverbindungen der Fettreihe, ein neue Klasse von organischen Körpern (Munich, 1886) summarizes his work on diazo compounds. A tribute to his teacher and predecessor at Heidelberg is Robert Bunsen als Lehrer in Heidelberg (Heidelberg, 1906). “Über das Diamid (Hydrazin),” in Berichte der Deutschen chemischen Gesellschaft, 20 (1887), 1632–1634, describes the discovery of hydrazine; and the discovery of hydrazoic acid is reported in “Über Stickstoff-wasserstoffsäure (Azoimid) N₃H,” ibid., 23 (1890), 3023–3033, and in “Azoimid aus Hydrazinhydrat and salpetriger Sä,” ibid., 26 (1893), 1263. Curtius’ early work on polypeptides is described in “Über einige neue der Hippursäure analog constituierte, synthetisch dargestellte Amidosäuren,” in Journal für praktische Chemie, 26 (1882), 145–208. On the reactions named for Curtius, see “Umlagerung von Säureaziden, RCON₃, in Derivate alkylirter Amine (Ersatz von Carboxyl durch Amid),” in Berichte der Deutschen chemischen Gesellschaft, 27 (1894), 778–781; “Ersatz von Carboxyl durch Amid in mehrbasischen Säuren,” ibid., 29 (1896), 1166–1167; “Umwandlung von Cholalsäure, C₂₃H₃₉O₃COOH, in Cholamin, C₂₃H₃₉O₃NH₂,” ibid., 39 (1906)), 1389–1391; and on coversion of an azide into an isocyanate, “Hippenyl isocyanat. C₆H₅CONHCH₂CNO,” in journal für praktische Chemie, 87 (1913), 513–541. Two papers by Curtius and Franzen dealing with plant chemistry are “Über die chemischen Bestandteile grüner Pflanzen,” in Justus Liebigs Annalen der Chemie, 390 (1912), 89–121; and “Das Vorkommen von Formaldehyd in den Pflanzen,” in Berichte der Deutschen chemischen Gesellschaft, 45 (1912), 1715–1718.

II. Secondary Literature. For biographical details and evaluations of Curtius’ work see the following (listed chronologically): August Darapsky, “Theodor Curtius zum 70. Geburtstag,” in Zeitschrift für angewandte Chemie, and Zentralblatt für technische Chemie, 40 (1927), 581–583; Heinrich Wieland, “Theodor Curtius,” ibid., 41 (1928), 193–194; C. Duisberg, “Theodor Curtius,” ibid., 43 (1930), 723–725; and August Darapsky, “Zum Andenken an Theodor Curtius,” in joürnal fur praktische Chemie, 125 (1930), 1–22.

A. Albert Baker, Jr.