st vĭl`hĕlm fən hôf`män), 1818–92, German organic chemist. He was professor at the Univ. of Berlin from 1865 and was a founder (1868) of the German Chemical Society. He studied the constitution of aniline and was the first to prepare rosaniline and its derivatives, thereby laying the basis for the aniline dye industry. He also discovered a reaction for deriving amines from amides and developed the Hofmann method of finding the vapor densities, and from these the molecular weights, of liquids. He also helped to popularize the concept of valence (the word comes from his term quantivalence).Hofmann, August Wilhelm von
Born Apr. 8, 1818, in Giessen; died May 5, 1892, in Berlin. German organic chemist.
A graduate of the University of Giessen, Hofmann was a student of J. von Liebig. In 1845 he was a privat docent at the University of Bonn. That same year he became the first director of the Royal College of Chemistry in London, which was founded that year and in which he worked for 20 years. From 1861 he was president of the London Chemical Society. From 1865 to 1892 he held the chair of chemistry at the University of Berlin. In 1868 he founded the German Chemical Society and its publication, and he remained president of the society until 1892.
In 1841, Hofmann discovered aniline and quinoline in coal tar, and in 1845 he isolated benzene from coal tar. By treating the benzene with a mixture of sulfuric and nitric acids he prepared nitrobenzene, and by reducing the latter with hydrogen he obtained aniline, thereby perfecting N. N. Zinin’s reaction. In 1850 he showed that it was possible to obtain amines by heating ethyl iodide (C2H5I) with ammonia. In 1881 he proposed a method of obtaining primary amines from amides of carboxylic acids (Hofmann reaction).
The work done by Hofmann and his school made possible the industrial processing of coal tar and the production of synthetic dyes. Hofmann synthesized a red aniline dye (fuchsine) in 1858 and established its composition in 1861. He identified the composition of various other dyes and obtained a number of triphenylmethane dyes.
In 1871, together with C. A. Martius, he discovered the rearrangement of the type
C6H5—NH—CH3 → CH3—C6H4—NH2
In 1881 he discovered a method of producing primary amines from acidic amides by treating them with bromine and alkalis.
WORKS
“Über eine sichere Reaktion auf Benzol.” Annalen der Chemie und Pharmacie, 1845, vol. 55, fasc. 2.REFERENCES
Schorlemmer, C. Vozniknovenie i razvitie organicheskoi khimii. Moscow, 1937. (Translated from English.)Volhard, J., and E. Fischer. August Wilhelm von Hofmann: Ein Lebensbild. Berlin, 1902.
D. V. LEBEDEV
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