Hans Meerwein

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Portrait of Hans Meerwein

Hans Leb (e) right Meerwein (born May 20, 1879 in Hamburg , † October 24, 1965 in Marburg ) was a German chemist . Meerwein was an organic chemist and discovered cationic rearrangement reactions as well as carbenes and an important alkylating reagent.

Life

Hans Meerwein was the son of Emil Meerwein , building senator and architect of the Hamburg stock exchange and the town hall.

Meerwein began studying chemistry in 1898 at the Fresenius Chemistry School in Wiesbaden , and later switched to the University of Bonn . There he received his doctorate in 1903 under Georg Schroeter (dissertation: On nitrated β-phenylglutaric acids and their reduction products ), followed this to the Technical University of Charlottenburg , today in Berlin. In 1905 Richard Anschütz and Ludwig Claisen offered him a position as a university assistant for the medical internship in Bonn. He completed his habilitation in 1908 with a thesis on condensation reactions - unsaturated aldehydes .

In 1914 he became adjunct professor in Bonn and finally an associate professor in 1922. In the same year he accepted a position as a full professor in Königsberg . In 1929 he finally succeeded Karl von Auwers at the University of Marburg , where he was director of the chemical institute until 1952 and where he worked as an emeritus scientist until 1965.

After the " seizure of power " by the National Socialists , on November 11, 1933, he signed the confession of the German professors to Adolf Hitler . From 1934 to 1939 he was a supporting member of the SS . In 1933 he was elected a member of the Leopoldina .

In 1945 the chemical institute in Marburg was largely destroyed by a bomb attack. Meerwein also lost his official residence in the institute and all of his belongings, including all scientific records and his private library. The new building at the same location was only inaugurated after his retirement in 1953.

His grave is in the Ohlsdorf cemetery in Hamburg.

plant

In his work after his habilitation, he dealt with problems of terpene chemistry and mechanistic problems of pinacol rearrangement. With very simple methods (pipette and burette ) and knowledge of the kinetics of reactions, he was able to safely deduce cationic (and not radical) intermediate stages in the pinacol rearrangement ( Wagner-Meerwein rearrangement ) and isoborneol - camphene rearrangement. After studying the acid-catalyzed rearrangement reaction of carbenium ions of (inexpensive) pinene, Meerwein developed a synthesis of camphor (rearrangements: pinene → camphene (or bornyl chloride) → isobornyl acetate → isoborneol → camphor (after oxidation)), which Schering soon used.

His fundamental work from 1922 on the Wagner-Meerwein rearrangement and the role of the norbornyl cation in the isoborneol-camphene rearrangement under consideration is seen as the foundation of physical-organic chemistry.

Because of the negative reactions of many colleagues to this work and the refusal of leading chemical journals to publish follow-up publications, he turned from the mechanistic study of reactions to pure organic synthesis, whereby he was more interested in new reagents and reactions than in the synthesis of complex molecules.

His works on anhydric acids were significant. Anhydrous acids (e.g. H [BF 4 ], H 2 [ZnCl 4 ]) are salt ions in organic solvents which, as catalysts for the formation of carbenium and oxonium ions, form particularly reactive intermediates.

His research on aluminum triisopropylate was of great scientific importance . It reacts in organic solvents with carbonyl compounds to form alcohols ( Meerwein-Ponndorf-Verley reduction ). This reduction has been successfully applied to many sensitive natural substances.

Using simple chemical reactions, Meerwein postulated the occurrence of carbenes and the polarizability of aromatic double bonds (also in benzene) in chemistry. During the bromination of benzene, a salt-like bromobenzene with a positive charge was formed in the meantime. If this is reacted with diazomethane , bromocycloheptatriene , a seven-membered ring , is obtained in high yield . Meerwein suspected that this reaction produced previously unknown reactive intermediates, the carbenes .

In Marburg, Hans Meerwein carried out fundamental work on synthetic and mechanistic organic chemistry and discovered carbocations , which was groundbreaking for the understanding of many organic-chemical reactions, especially for polymerization reactions . Through his research he became one of the founders of physical organic chemistry, who used reaction kinetics to elucidate reaction mechanisms.

Later he discovered in the reaction of boron trifluoride etherate with epichlorohydrin the triethyloxonium tetrafluoroborate (Meerwein reagent, Meerwein salts ). Many complicated natural product syntheses could be carried out with this alkylating reagent. In this context, he also did pioneering work in polymer chemistry: ring-opening polymerization of tetrahydrofuran and the first production of linear polyethylene (before the Ziegler-Natta process ), the Meerwein methylation with diazomethane. They called it polymethylene at the time, and Meerwein's priority played a role in patent disputes between Karl Ziegler and DuPont in the 1950s .

The aryldiazonium salts used for Meerwein arylation of the α, β-unsaturated carboxylic acids (replacement of the carboxy group through the aromatics, Meerwein Schustersche stilbene).

Commemorative plaque of the Society of German Chemists at the Old Chemical Institute of the Philipps University of Marburg

The following important reactions are linked to his name:

Awards

literature

Web links

Individual evidence

  1. ↑ Life data, publications and academic family tree of Hans Meerwein at academictree.org, accessed on January 2, 2019.
  2. ^ Ernst Klee : The dictionary of persons on the Third Reich. Who was what before and after 1945 . Fischer Taschenbuch Verlag, second updated edition, Frankfurt am Main 2005, ISBN 978-3-596-16048-8 , p. 399.
  3. ↑ Hess. Main State Archive Wiesbaden, Dept. 483 No. 4645d; Section 529 / Ma-B No. 1175, sheet 1 and 11.
  4. ↑ H. Meerwein, Konrad van Emster: About the equilibrium isomerism between bornyl chloride, isobornyl chloride and camphene chlorohydrate , reports of the German Chemical Society, Volume 55, 1922, p. 2500
  5. ↑ GA Olah: Crossing Conventional Boundaries in Half a Century of Research, Journal of Organic Chemistry, Volume 70, 2005, p. 2428. Olah calls Meerwein his role model as a chemist because of his versatility.
  6. ^ Olah, Journal of Organic Chemistry, Volume 70, 2005, p. 2428
  7. ↑ Meerwein, D. Delfs, H. Morschel, Die Polymerisation des Tetrahydrofurans, Angewandte Chemie, Volume 72, 1960, pp. 927-934
  8. ↑ H. Meerwein, W. Burneleit, On the action of diazomethane on ketones in the presence of catalysts I, Ber. Deutsche Chemische Gesellschaft, Volume 61, 1928, pp. 1840-1847
  9. ↑ Heinz Martin, Polymers, Patents, Profits: A Classic Case Study for Patent Infighting, Wiley-VCH, 2007, p. 120
  10. ^ Department of Chemistry at the University of Marburg
personal data
SURNAME Meerwein, Hans
ALTERNATIVE NAMES Meerwein, Hans Leberecht (full name)
BRIEF DESCRIPTION Chemist
DATE OF BIRTH May 20, 1879
PLACE OF BIRTH Hamburg
DATE OF DEATH October 24, 1965
Place of death Marburg