Hans Meerwein
Hans Leb (s) right Meerwein ( born May 20, 1879 in Hamburg, † October 24, 1965 in Marburg ) was a German chemist. Meerwein was an organic chemist and has discovered cationic rearrangement reactions as well as carbenes and an important alkylating reagent.
Life
Hans Meerwein was the son of Emil Meerwein, senator and architect of the Hamburg Stock Exchange and City Hall.
His study of chemistry began Meerwein in 1898 at the School of Chemistry Fresenius in Wiesbaden, later he moved to the University of Bonn. There he earned his doctorate at Georg Schröter, followed this to the Technical University of Charlottenburg in Berlin today. 1905 offered him Richard Anschütz and Ludwig Claisen in Bonn a position as assistant professor for the medical internship at. He habilitated in 1908 with a thesis on the Michael condensation.
In 1914, he was Adjunct Professor in Bonn and in 1922 finally associate professor. In the same year he accepted an appointment as a full professor in Konigsberg. 1929 finally he succeeded Karl von Auwers at the University of Marburg, where he was director of the chemistry department until 1952 and as a professor emeritus until 1965 worked scientifically.
After the " seizure of power" of the Nazis, he was on 11 November 1933, the signatories of the commitment of the professors at German universities and colleges to Adolf Hitler and the Nazi state. From 1934 to 1939 he was a supporting member of the SS
In 1945, the Chemical Institute in Marburg was largely destroyed by a bomb attack. Meerwein, thus losing his official residence on the Institute and its possessions, including all academic records and his private library. The new building on the same site was not dedicated until after his retirement in 1953.
His grave is in the cemetery Ohlsdorf in Hamburg.
Work
In his work after his habilitation he dealt with problems of terpene chemistry and mechanistic problems for pinacol rearrangement. With very simple methods ( pipette and burette ) and the knowledge of the kinetics of reactions he could safely close to cationic (rather radical ) intermediates in the pinacol rearrangement ( Wagner -Meerwein rearrangement) and isoborneol - camphene rearrangement. Meerwein developed after studying the acid-catalyzed rearrangement reaction of carbenium ions of the ( inexpensive ) pinene a synthesis of camphor ( rearrangements: pinene → camphene (or bornyl ) → Isobornylazetat → isoborneol → camphor (after oxidation) ), which was used at Schering soon.
Furthermore, significant of his works to the anhydrous acids have been. Anhydrous acids ( e.g., H [BF4 ], H2 [ ZnCl4 ] ) are salt ions in organic solvents which form, as catalysts for the formation of carbonium, oxonium ions and particularly reactive intermediates.
Of high scientific importance were his research with aluminum isopropoxide. These react in organic solvents with carbonyl compounds to alcohols ( Meerwein Ponndorf - Verley reduction ). In many sensitive natural products, this reduction has been applied with success.
Meerwein postulated by simple chemical reactions, the occurrence of carbenes and the polarizability of the aromatic double bonds ( in benzene ) in chemistry. In the bromination of benzene was formed in the meantime, a salt-like bromobenzene with a positive charge. Substituting this with diazomethane to, we obtain in high yield bromo- cycloheptatriene, a seven-membered ring. Meerwein assumed that in this reaction so far unknown reactive intermediates carbenes formed.
In Marburg, Hans Meerwein carried out fundamental work on synthetic and mechanistic organic chemistry and discovered the carbocations, which was groundbreaking for the understanding of many organic reactions, particularly for polymerization reactions. He was one of the founders of physical organic chemistry, which started the reaction kinetics for the elucidation of reaction mechanisms through his research.
Later he discovered the reaction of boron trifluoride etherate and epichlorohydrin the triethyloxonium ( Meerwein 's reagent, Meerwein salts). This alkylating many complex natural product syntheses could be carried out.
The aryl diazonium salts used for Meerwein arylation of α, β -unsaturated carboxylic acids ( replacement of the carboxyl group by the aromatics, Meerwein Schustersche stilbene ).
The following important reactions are associated with his name:
- Wagner- Meerwein rearrangement
- Meerwein - methylation
- Meerwein arylation
- Meerwein - Verley reduction Ponndorf