August Wilhelm von Hofmann

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August Wilhelm von Hofmann
Photo after the painting by Heinrich von Angeli
Grave in the Dorotheenstadt cemetery

August Wilhelm Hofmann , von Hofmann from 1888 (born April 8, 1818 in Gießen , † May 5, 1892 in Berlin ), was a German chemist and a decisive pioneer in the research of aniline dyes in England and Germany. He developed a variety of important conversion methods in organic chemistry and founded the German Chemical Society .

Live and act

Hofmann's father was an architect and had built the laboratory building for Justus von Liebig .

August Wilhelm Hofmann initially studied law in Giessen, but changed his wish to study when he attended Justus von Liebig's chemistry lectures from 1836 . Hofmann became Liebig's assistant and received his doctorate in 1841 with a thesis on the " chemical investigation of organic bases in coal tar ". Hofmann's first studies dealt with the purification and elemental analysis of aniline (kyanol) and quinoline (leucol) obtained from coal tar . After his habilitation in Gießen in 1845, he briefly went to the University of Bonn as a private lecturer in chemistry .

At the recommendation of Liebig and at the request of the English Prince Consort Albert , however, he took over a professorship at the Chemical Institute of the Royal School of Miners in London that same year . This professorship in London filled twenty years of his life, during which he later had very important students in the field of tar paints and other material synthesis ( William Henry Perkin , William Crookes , Carl Alexander von Martius , Johann Peter Grieß , Charles Blachford Mansfield (1819–1855), Sir Frederick Abel , Edward Chambers Nicholson (1827-1890)). He and his students played an important role in the development and commercial exploitation of the tar dye chemistry for textile dyeing. Tar was previously only a worthless waste product from coke extraction from hard coal, but then it became the most important raw material for industrial organic chemistry .

He was entrusted with the establishment of the Royal College of Chemistry in London, the direction of which was entrusted to him upon completion, and where he trained numerous English and German chemists. The royal family also attended Hofmann's lectures and had him perform experiments. Especially the scientifically interested Princess Viktoria , later as the wife of Frederick III. Queen of Prussia and German Empress , Hofmann remained on friendly terms and ensured that he was later ennobled. Hofmann played a key role in the preparations for the World Exhibition in 1851 and the World Exhibition in 1862 in London.

From 1845 Hofmann was a member of the first chemical society, the Chemical Society founded in London in 1841, from 1847 to 1861 he was Foreign Secretary, from 1861 to 1863 its President (board of directors) and finally in 1863 Vice President. He spoke four languages ​​and he edited the English Journal of the Chemical Society from 1851 to 1864 . He also published some of his own research results in the German Liebig's Annalen der Chemie und Pharmacie .

After the early death of the English prince consort, he was offered a position in Bonn in 1863 and the Poppelsdorf Palace was converted into a chemical institute according to his plans. Ultimately, Hofmann turned down the call to the University of Bonn and instead accepted the call to the immensely rebuilt Friedrich Wilhelms University in Berlin in 1864 . From May 1865 he held lectures in inorganic and organic chemistry at the I. Chemical Institute at Georgenstrasse 34-36. He stayed in Berlin until his death in 1892.

He illustrated chemistry through contemporary experiments, in doing so he developed the Hofmann decomposition apparatus and wrote a textbook for chemistry.

Hofmann founded the German Chemical Society in Berlin in 1867 together with Adolf Baeyer , CA Martius , C. Scheibler and E. Schering , H. Wichelhaus based on the model of the British Chemical Society . Hofmann was elected to the board (president) every two years as a founding member. The reports of the Chemical Society were sent to members and, for a fee, to universities; Hofmann wrote most of the articles himself. In 1873 Hofmann was elected a member of the Leopoldina . Since 1853 he was a member of the Prussian Academy of Sciences , since 1855 of the Bavarian Academy of Sciences and since 1860 of the Göttingen Academy of Sciences .

Between 1870 and 1900 there were controversies about the training of chemists in the German Empire. The number of students increased. Many practice-oriented technical universities emerged. A decision had to be made on the right to award doctorates for technical universities. The entry requirements for the course were different (high school, secondary school). Industry representatives wanted a state examination, more practical research work, university lecturers wanted to receive free research and the university's internal examination.

Hofmann mediated between the various interests, as Berlin industry representatives such as Martius, Hugo Kuenheim and Ernst Schering were among the members.

In 1886 Hofmann became chairman and first president of the Society of German Natural Scientists and Doctors .

On his 70th birthday (1888) he was raised to the Prussian nobility. The Hofmann Foundation was established in his honor by the German Chemical Society .

On May 5, 1892 von Hofmann had given another lecture, chaired a faculty meeting, and chaired two final exams for doctoral students. At 9 o'clock in the evening he left the university in a good mood. After dinner he began to feel unwell, the doctors who were called could no longer help him, and von Hofmann died.

His grave is in the Dorotheenstadt cemetery .

Emil Fischer von Würzburg was appointed to Berlin as his successor in 1892 . As in Würzburg, he designed a new institute building in Berlin with its own service villa, which was moved into from 1900 in Hessische Strasse 1/2.

family

On August 12, 1846, in Darmstadt, he married Helene Moldenhauer (* August 12, 1823 - February 6, 1852), the daughter of the manufacturer and chemist in Bingen, Louis Moldenhauer and Louise Strecker . Then he married on December 13, 1856 in Wandsworth Rosamond Margaret Jane Wilson (born February 11, 1838, † January 30, 1860). After her death, he married on March 12, 1866 in Aschaffenburg Elise Barbetta Moldenhauer (* December 31, 1845 - October 17, 1871), the daughter of the manufacturer and chemist from Bingen Georg Moldenhauer and Helene Charlotte Strecker . His last wife was Auguste Wilhelmine Berta Tiemann (born February 13, 1854 - November 8, 1922) in Blankenburg on August 11, 1873 , the sister of his assistant Ferdinand Tiemann (1848–1899). He had several children including:

  • Albert (September 30, 1867 - March 11, 1940), historian ∞ Paula Meidinger

Scientific work

The early chemists only had elemental analysis, melting point, boiling point and refractive index available for substance analysis and pure representation. At that time there was no knowledge of structural formulas, laws of valences, knowledge of functional groups, reactivities or bonding abilities. These had to be thought out first. Von Hofmann had many English and German employees who supported him in his research. Von Hofmann is considered an outstanding pioneer in organic chemistry.

In his first work in 1843 Hofmann dealt with bases of coal tar. He determined the identity of the aniline found from the anthranilic acid with the substance kyanol in coal tar. By adding chemical reagents (hypochlorous salts) to the aniline, Hofmann found strongly colored solutions and strongly colored crystals. He substituted the hydrogen atoms with chloric, bromic and hydroiodic acid and was thus able to confirm the radical theory of Jean Baptiste Dumas and Auguste Laurent . The elemental analysis and properties of the leucol were identical to the quinoline , which Charles Frédéric Gerhardt had obtained from quinine . Hofmann developed a synthesis of aniline based on benzene, which was abundant in coal tar.

Hofmann first described the exact course of the extraction of benzene from coal tar and transferred the extraction of benzene to Mansfield. Together with Muspratt he discovered toluidine , with J. Blyth he investigated styrene and with the nitration process they improved (a mixture of concentrated sulfuric acid and nitric acid, the most common nitration method today) succeeded in producing 1,3-dinitrobenzene .

Hofmann investigated the reaction of cyanogen chloride with aniline and obtained urea derivatives of aniline or diphenylguanidine when reacted with organic bases .

For a deeper understanding, Hofmann examined the amino group of aniline. According to Jöns Jakob Berzelius and the previous theory of his time, only one hydrogen atom could be replaced by an organic group (radical) in both aniline and ammonia. After unsuccessful attempts to convert phenol with aniline, Hofmann tried the conversion of aniline with ethyl iodide . He found ethylaniline and diethylaniline and soon afterwards investigated the reaction of ethyl iodide with ammonia. In this case, even three products could be obtained: monoethylamine, diethylamine and triethylamine . Hofmann was now able to show that, in addition to carbon and oxygen, the nitrogen atom could also be substituted by radicals (organic groups or halogens). With this he supported the substitution theory of Jean Baptiste Dumas .

A short time later, Hofmann discovered the strange fact that even with the complete exclusion of water, a salt was formed when aniline was reacted with ethyl iodide. The elemental analysis confirmed the result that this compound was an organic salt called tetraethylammonium iodide. Various tetralkylammonium compounds have now been prepared and heated. It was found that ethene was split off as a gas from tetraethylammonium iodide and the triethylamine could be recovered. With other salts too, alkene splitting off occurred when heated. In honor of the discoverer, this reaction is called Hofmann's elimination. Only in the case of the tetramethylammonium salt was no gas formation after heating, but methanol and the trimethylamine were formed .

Hofmann later discovered another important reaction regarding primary amides (Hofmann degradation, Hofmann rearrangement ). If the amides were exposed to a solution of bromine and sodium hydroxide solution, one hydrogen of the amide group was replaced by a bromine atom. Hydrogen bromide was split off and an isocyanate was formed . This compound is converted to a carbamic acid and then to the primary amine under basic conditions . In this reaction the amide carbon atom is lost as carbon dioxide. One carbon atom in a linear chain can be successively removed. With this method Hofmann was able to break down the nonanoic acid down to the amide of valeric acid .

Other important fields of work were: Production of sulfonic acids (e.g. methanedisulfonic acid, benzene disulfonic acid), allyl alcohol and derivatives. With A. Cahour he developed improved syntheses of trimethylphosphine , triethylphosphine from phosphorus trichloride and the zinc alkyls; they also found quaternary tetraalkylphosphonium compounds and trialkylphosphine oxides.

Later he turned to the hemlock ingredient coniin , found an elimination reaction of the alkylated piperidine ( Hofmann elimination ).

He discovered hydrazobenzene and the strange internal rearrangement in benzidine and was able to detect formaldehyde from the oxidation of methanol with platinum oxide.

Hofmann also found new dyes; A triarylmethane dye (para-rosaniline) was formed from carbon tetrachloride and aniline when heated. Hofmann recognized that fuchsine and rosaniline are derivatives of triphenylmethane and that carbon tetrachloride acts as a connecting substance in the reaction. Treatment of rosaniline with triethyl iodide gave rise to a strong dye, triethylrosaniline ( Hofmann's violet , an important purple dye for many years). Hofmann later clarified the structure of aniline yellow and the quinoline dyes quinoline red, quinoline yellow , and cyan blue.

The Hofmann decomposition apparatus and the Hofmann rearrangement of carboxamides are named after von Hofmann , as well as the Hofmann rule for intramolecular eliminations (= Hofmann elimination ) with sterically demanding bases.

Honors

Memorial in the Hofmann House
Duplicate of the memorial plaque for August Wilhelm von Hofmann, donated by the Siemens-Ring Foundation (* 1916) and unveiled on July 8, 1918 at the house where he was born in Gießen, reconstructed by the Werner-von-Siemens-Ring Foundation .

The Royal Society awarded him the Royal Medal in 1854 and the Copley Medal in 1875 . In 1859 he was elected to the Académie des Sciences and in 1862 to the American Philosophical Society , in 1877 to the American Academy of Arts and Sciences and in 1887 to the National Academy of Sciences . From 1883 von Hofmann was a member of the Pour le mérite for science and the arts .

In 1900, the Hofmann House (Sigismundstrasse 4 in Berlin) was built in his honor according to plans by Otto March . and became the seat of the German Chemical Society until 1945. A "Hofmannhaus-Gesellschaft mbH" with 600,000 Mk share capital (from industrial donations) was founded in 1898 to finance it.

The Society of German Chemists awards the August-Wilhelm-von-Hofmann medal to “chemists ... who have made special contributions to chemistry” .

There is a memorial plaque in his hometown of Giessen.

literature

Individual evidence

  1. ↑ a b c d e f g h Günther Bugge: Das Buch der Grossen Chemiker, Volume 2, Verlag Chemie GmbH reprint from 1955, p. 136 ff.
  2. ↑ later printed in full as: Dr. August Wilhelm Hofmann, Chemical investigations of the bases in hard coal tar oil in Annalen der Chemie und Pharmacie 47 , 37-87 (1843).
  3. ↑ Ernst Bäumler: The red factory . R. Piper GmbH & Co. KG, Munich 1988, ISBN 3-492-10669-2 , p. 28 f .
  4. ^ History of the Chemical Society of London Jubilee Volume 1891
  5. ^ "Old chemistry" in Poppelsdorfer Schloß ( Memento from July 11, 2014 in the Internet Archive )
  6. ^ Board members 1868, 69, 73, 75, 76, 79, 82, 83, 85, 87, 88, 90 and 92, otherwise vice-presidency. Source: Report of the German Chemical Society - minutes of the January meeting of the current year.
  7. ↑ Holger Krahnke: The members of the Academy of Sciences in Göttingen 1751-2001 (= Treatises of the Academy of Sciences in Göttingen, Philological-Historical Class. Volume 3, Vol. 246 = Treatises of the Academy of Sciences in Göttingen, Mathematical-Physical Class. Episode 3, vol. 50). Vandenhoeck & Ruprecht, Göttingen 2001, ISBN 3-525-82516-1 , p. 116.
  8. ↑ Christoph Meinel and Hartmut Scholz The Alliance of Science and Industry August Wilhelm Hofmann (1818 - 1892) , Verlag Chemie VCH Weinheim, p. 221 ff.
  9. ^ Condolence of the Chemical Society of London on the death of AW Hofmann, digitized on Gallica
  10. ↑ Ann. d. Chem. 69 , 162 (1849)
  11. ↑ Dear. Ann. d. Chem. 53 , (1845), pp. 221-229
  12. ↑ Dear. Ann. 53 , Issue 3 (1845), pp.289-329, AW Hofmann, John Blyth On styrene
  13. ↑ Ann. d. Chem. 70 , 129-149 (1849)
  14. ↑ Ann. d. Chem. 74 , 117 (1850) .
  15. ↑ Ann. d. Chem. 74 , 139 (1850) .
  16. ^ Report of the German Chemical Society, 14 , 2725 (1881). ( Digitized on Gallica )
  17. ^ Report of the German Chemical Society, 15 407 (1882). ( Digitized on Gallica )
  18. ^ Report of the German Chemical Society, 15 752 (1882). ( Digitized on Gallica )
  19. ^ Report of the German Chemical Society, 15 762 (1882). ( Digitized on Gallica )
  20. ^ Report of the German Chemical Society, 17 , 1406 (1884). ( Digitized on Gallica )
  21. ↑ Ann. d. Chem. 100 , 129 (1856) .
  22. ↑ Ann. d. Chem. 102 , 285 (1857) .
  23. ↑ Ann. d. Chem. 104 , 1-39 (1857) .
  24. ^ Proc. Roy. Soc. 9 , 284 (1858) .
  25. ^ Proc. Roy. Soc. 12 , 2 (1862) .
  26. ^ Proc. Roy. Soc. 13 , 13 (1863) .
  27. ^ Member History: August W. von Hofmann. American Philosophical Society, accessed October 2, 2018 .
  28. ↑ Special article in Reports of the German Chemical Society, 1900 ( digitized on Gallica )
  29. ↑ DChG General Assembly December 16, 1898 ( digitized on Gallica )

Web links

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personal data
SURNAME Hofmann, August Wilhelm von
ALTERNATIVE NAMES Hofmann, August Wilhelm
BRIEF DESCRIPTION German chemist
DATE OF BIRTH April 8, 1818
PLACE OF BIRTH to water
DATE OF DEATH May 5, 1892
Place of death Berlin