August Wilhelm von Hofmann
August Wilhelm (from) Hofmann ( born April 8, 1818 in Giessen, † May 5, 1892 in Berlin) was a German chemist. Hofmann From the pioneer of the study of aniline dyes in England and Germany has been. He has a number of important conversion methods in organic chemistry developed and founded the German Chemical Society.
Life and work
Hofmann's father was an architect and had built the laboratory building for Justus von Liebig.
August Wilhelm Hofmann studied in Giessen law, changed his academic dreams when he visited in 1836 chemistry lectures of Justus von Liebig. Hofmann was Liebig's assistant, received his doctorate in 1841 with him and went after his habilitation in 1845 as a lecturer in chemistry at the University of Bonn. The first studies Hofmann dealt with the cleaning and elemental analysis of the product obtained from coal tar aniline ( Kyanol ) and quinoline ( Leukol ).
On the recommendation of Liebig and at the request of the British Prince Consort Albert, he took over the same year a professor at the Chemical Institute of the Royal School of Miners in London. This professorship in London completed twenty years of his life, where he many later very important students in the field of coal-tar dyes and other product syntheses ( William Henry Perkin, William Crookes, Carl Alexander von Martius, Johann Peter semolina, Charles Blackford Mansfield ( 1819-1855 ), Sir Frederick Abel, Edward Chambers Nicholson (1827-1890)) had. He and his students played a major role in the development and commercial exploitation of Teerfarbstoffchemie for textile dyeing. Tar was previously only a worthless waste product of Koksgewinnung from coal, but was then the most important raw material for the industrial organic chemistry.
He was charged with the establishment of the College of Chemistry in London, its management was transferred to him after completion, and where he trained numerous English and German chemist. The young Queen Victoria (United Kingdom) attended Hofmann's lectures. Amicable they remained connected Hofmann and made sure that he was later knighted and a bust of him was erected ( next to the statue of Victoria) at the Brandenburg Gate. Hofmann was heavily involved in the preparations for the World's Fairs in 1851 and 1862 in London.
Since 1845 Hofmann was a member of the first chemical company, which was founded in 1841 Chemical Society of London, from 1847 to 1861 he was foreign secretary, from 1861 to 1863 the President (Chief Executive ) and most recently in 1863 Vice President. He mastered four languages and presented in this time before the Chemical Society many results, which were published but then in Liebigs Annalen.
After the early death of the English Prince Consort in 1863, he received a call to Bonn and allowed Poppelsdorf Palace according to his plans to rebuild a chemical institute. Ultimately rejected Hofmann from the chair at the University of Bonn and instead took in 1864 the call to the immense converted Friedrich- Wilhelms- University of Berlin. From May 1865 he held the I. Chemical Institute at the George Street 34-36 lectures in inorganic and organic chemistry. He remained until his death in Berlin in 1892.
He illustrated the chemistry by contemporary experiments, while he developed the Hofmann decomposition apparatus and wrote a textbook on chemistry.
Hofmann founded in 1867, along with Adolf Baeyer, CA Martius, C. Scheibler and E. Schering, H. Wichelhaus modeled after the British Chemical Society, the German Chemical Society of Berlin. Hofmann was elected as a founding member of two annually to the Executive Board (President). The reports of the Chemical Society were sent to members for a fee at universities; Hofmann did much of the article itself
Between 1870 and 1900, there was controversy over the chemist training in the German Reich. The number of students increased. It created a lot of hands-on technical universities. Was to decide on the right to award doctorates of Technical Colleges. The entrance requirements for the program were different (Gymnasium, Realschule). Industry representatives wanted a state examination, more practical research, university teacher wanted to get the free research and the university internal audit.
Hofmann mediated between the different interests, as well as Berlin's industry leaders such as Martius, Hugo Kuenheim, Ernst Schering were among the members.
In 1886, Hofmann became chairman and first president of the Society of German Natural Scientists and Physicians.
On his 70th birthday (1888 ), he was elevated to the Prussian nobility. From the German Chemical Society him the Hofmann Foundation was set up in honor.
Hofmann was married four times; three of his wives died young. He had 11 children.
On May 5, 1892 had by Hofmann nor a lecture held a faculty meeting passed two final degrees led by graduate students. Evening at 9 clock he left in a cheerful mood the university. After dinner, malaise set in, the summoned doctors could no longer help him, passed by Hofmann.
His grave is located on the Dorotheenstädtischer cemetery.
He was succeeded yet called 1892 Emil Fischer from Würzburg to Berlin. As in Würzburg also he designed in Berlin a new institute building with its own official residence, which was based in Hessischestrasse 1/2 from 1900.
Scientific work
The early chemists had for material analysis and purification of only the elemental analysis, melting, boiling point, refractive index. There were no knowledge of structural formulas, laws of valences, knowledge of functional groups, reactivity or binding capabilities. These had first to be devised. From Hofmann many English and German people who supported him during the excavations had. From Hofmann was considered outstanding pioneer of organic chemistry.
In his first works in 1843 Hofmann dealt with bases of Steinkohleteers. He represents determine the identity of the found from the anthranilic acid aniline with the substance of the Kyanol Steinkohleteers. The addition of chemical reagents ( hypochlorous salts ) for aniline Hofmann was strongly colored solutions and highly colored crystals. With chlorine, bromine and hydriodic he substituted the hydrogen atoms and can confirm that the free radical theory of Jean Baptiste Dumas and Auguste Laurent. The Leukol was by elemental analysis and properties identical in the quinoline, which was obtained from Charles Frederic Gerhardt 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 recovery of benzene Mansfield. Together with Muspratt he discovered the toluidine, with J. Blyth, he examined the styrene and with the of them improved nitration method (a mixture of concentrated sulfuric acid and nitric acid, most commonly used today nitration method) was able to produce the 1,3-dinitrobenzene.
Hofmann examined the reaction of cyanogen chloride with aniline and received upon reaction with organic bases urea derivatives of aniline or the diphenyl.
To better understand Hofmann examined the amino group of aniline. After Jöns Jakob Berzelius and the recent theory of his time only one hydrogen atom by an organic group ( radical) could be replaced in both the aniline as in ammonia. After unsuccessful attempts by the reaction of phenol with aniline Hofmann tested the reaction of aniline with ethyl iodide. He found Ethylaniline and diethylaniline and examined soon after the conversion of ethyl iodide with ammonia. In this case, even were three products are obtained: monoethyl amine, diethylamine and triethylamine. Hofmann has now shown that in addition to carbon and oxygen and the nitrogen atoms could be substituted by radicals ( organic groups or halogens ). He supported the theory of substitution of Jean Baptiste Dumas.
A short time later, Hofmann discovered the remarkable fact that even with a complete exclusion of water a salt in the reaction of aniline with ethyl iodide was. According to the elemental analysis confirmed the result that it is this compound is an organic salt, tetraethylammonium iodide, acted. There have now been presented and heated different Tetralkylammoniumverbindungen. It was found that split off as a gas from tetraethylammonium ethene and the triethylamine could be recovered. Other salts were Alkenabspaltungen on when temperature rises. This reaction is to honor the discoverer, Hofmann elimination called. Only the tetramethyl ammonium salt of any gas formation occurred upon heating, but formed methanol, and the trimethylamine.
Later Hofmann discovered another important reaction with respect to primary amides ( Hofmann degradation Hofmann rearrangement). , On discontinuation of the amides of a solution of bromine and sodium hydroxide, it was a hydrogen of the amide group is replaced by a bromine atom. Hydrogen bromide was cleaved and formed an isocyanate. 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. It can be successively remove a carbon atom in a linear chain. Hofmann was able to reduce with this method, the nonanoic acid to the amide of valeric acid.
Other important areas of work were: Preparation of sulfonic acids (eg methanedisulphonic benzenedisulfonic ), allyl alcohol and derivatives. With A. Cahour he developed improved syntheses of trimethylphosphine, triethylphosphine from phosphorus trichloride and zinc alkyls, they also found quaternary tetraalkyl compounds and Trialkylphoshinoxide.
Later he turned to the hemlock ingredient coniine, found an elimination reaction of the alkylated piperidine ( Hofmann elimination ).
He discovered the hydrazobenzene and the strange inner rearrangement to benzidine and can detect the formaldehyde from the oxidation of methanol with platinum oxide.
Also, new dyes found Hofmann; of carbon tetrachloride and aniline formed upon heating a triaryl methane dye (para- rosaniline ) .. Hofmann realized that fuchsin and rosaniline are derivatives of triphenylmethane and participates carbon tetrachloride as a linking material in the reaction. For the treatment of Rosanilins Triethyliodid with a strong dye, the Triethylrosanilin formed ( Hofmann violet, for many years an important violet dye). Later Hofmann explained to the structure of aniline and quinoline yellow Chinolinrot, quinoline yellow, cyan.
According to Hofmann Hofmann decomposition apparatus and the Hofmann rearrangement of carboxamides are named, as well as the Hofmann rule for intramolecular eliminations ( = Hofmann elimination ) with bulky bases.
Honors
From the Royal Society, he was in 1854 awarded the Royal Medal, 1875 with the Copley Medal. Since 1883 was of a member of the Pour le Mérite Hofmann of Science and Arts.
In 1900 him the Hofmann -Haus ( Sigismundstraße 4 in Berlin) was built in honor, designed by Otto March. The house that no longer stands today, the seat of the German Chemical Society, the Hofmann had been founded.
The German Chemical Society awards " to chemists [ ... ] who have rendered special services to chemistry " August- Wilhelm -von- Hofmann Medal.