Georg Wittig

Georg Friedrich Karl Wittig ( born June 16, 1897 in Berlin, † 26 August 1987 in Heidelberg ) was a German chemist and recipient of the Nobel Prize for Chemistry in 1979 Wittig found a way to the carbonyl group of an aldehyde or ketone in the carbon-carbon. double bond of an alkene with any substituent convert.

Life

Wittig was the son of a professor of the School of Applied Arts in Kassel, and his mother was gifted musically. Wittig had the artistic talent from both parents, he played the piano very well, could also compose and paint very well. He attended the Wilhelm Gymnasium in Kassel through high school and began in 1916 at age 19 to study chemistry in Tübingen. However, he was called shortly thereafter and fell into British captivity. From 1919, he studied chemistry in Marburg. There Wittig was the chemical institute at Karl Friedrich von Auwers and a doctorate on May 7, 1923.

In the same year he got a job as a teaching assistant at the University of Marburg. He married Waltraud Ernst. After his habilitation in 1926, he worked with Hans Meerwein as senior assistant. In 1932 he became department head and associate professor at the Technical University Braunschweig.

1933 Wittig was a member of the SA. 1937 brought him Hermann Staudinger at his institute in Freiburg im Breisgau; In the same year Wittig joined the NSDAP. Wittig was tenured in 1939 and from 1944 he was a full professor at the University of Tübingen. From 1956 worked as director of the Wittig organic- chemical Institute of the University of Heidelberg.

He was an honorary citizen of the city of Heidelberg.

Scientific work

Wittig dealt first with organic radicals. He established hexaphenylethane and suspected a biradical structure. However, this structure could not be confirmed. For the introduction of phenyl groups Wittig used the phenyllithium. A simple method of preparation of phenyllithium was found in 1930, Karl Ziegler from bromobenzene and butyl lithium. The anionic phenyl proved to be very strong Phenylierungsreagenz, let it react with bromobenzene to biphenyl. The binding of carbon-lithium is very strongly polarized. Wittig postulated due to the present reactions, the benzyne ( see picture).

Later Wittig interested for other carbon groups with an anionic charge on carbon and a positive charge. He deprotonated tetramethylammonium ion with phenyllithium and got amine ylides. The name refers to the ylide ionic charge in a molecule. The nitrogen usually has only three bonds to neighboring atoms. Deprotonation with phenyllithium on a negative carbon atom adjacent to the positive nitrogen was generated. These ylides can attach to polar bonds easily. In the presence of benzophenone amine gave ylides readily characterizable salts, wherein the negatively charged carbon of the ylide associated with the positively polarized carbonyl carbon. Very similar to the nitrogen, the phosphorus. Already August Wilhelm von Hofmann continued his successful investigations of amines proceeds with phosphines. This path also went Wittig and had success.

In the reaction of triphenylphosphine with methyl iodide quaternary phosphonium salt is formed. With phenyllithium this salt can be deprotonated to ylene Triphenylphosphinmethylen. Unlike the nitrogen with phosphorus resonance structure can be formulated with a double bond between the methyl group and the phosphorus ( ylene ).

In implementing this Ylens with benzophenone Wittig discovered in 1954, now the formation of diphenylethylene and the elimination of triphenylphosphine oxide. With the deprotonated Triphenylphosphinmethylen settled as a result, carbonyl oxygen replaced by a methyl group. Instead of a simple methyl group could replace the oxygen atom of the carbonyl group with other Ylidsalzen complicated carbon structure. 10 years after Wittig's discovery more than 70 patents had already been submitted for nutrient cycling and natural product synthesis with the Wittig reaction. Wittig had his great discovery at a later age, with 57 years.

Around 1950 he came with his doctoral Ulrich Schöllkopf a generally applicable synthesis of olefins, which are named after him Wittig reaction; for he received in 1979, together with Herbert Charles Brown, who worked in the area of the boranes, the Nobel Prize for Chemistry.

Wittig reaction with, inter alia, large scale of retinol (vitamin A) is prepared. On a laboratory scale, it is one of the most important reactions for the production of C = C double bonds. Carbonyl compounds and phosphorus ylides are reacted in an addition -elimination sequence with each other.

According to him, the 1,2- Wittig rearrangement was named.

Honors

Works

• Preparative chemistry. Springer, Berlin 1976, ISBN 3-540-07932-7
• Stereochemistry. Akad Verlagsges., Leipzig 1930.
• About ate complexes as reactive intermediates directing. Westdt. Verl, Cologne 1966.
• Studies on a- oxydiphenyl and the formation of diphenoquinones. Univ. Dissertation, Marburg 1923.
• To tap the benzo - gamma - pyrone. Habilitation Thesis, Marburg 1926.
• With Ulrich Schöllkopf: About triphenylphosphine - methylene as olefin-forming reagents. Ber. d Dt. Chem Ges 87 (9): pp. 1318-1330, 1954.