Arbusov reaction
The Arbusow reaction or Michaelis-Arbusow reaction [frequently found alternative spelling Arbusov ] is a name reaction in organic chemistry . It was named after the Russian chemist Alexander Jerminingeldowitsch Arbusow (Russian: Александр Ерминингельдович Арбузов , 1877-1968) and the German chemist August Michaelis (1847-1916). By reacting a nucleophilic, trivalent phosphorus compound with a haloalkane, a pentavalent phosphorus compound with a new phosphorus-carbon bond is obtained.
The Arbusow reaction proceeds according to an S N 2 mechanism . The starting compound is first converted into the quaternary phosphonium salt by alkylation on trivalent phosphorus. By attack of the nucleophilic counterion on an alkoxy group, this less stable intermediate is converted into the more stable pentavalent phosphorus compound with elimination of an alkyl halide:
- Mechanism of the Arbusow reaction with X = −Br, −I; Y, Z = −O − R, −R
Another driving force is the distillative removal of the resulting alkyl halide from the reaction equilibrium, which often takes place during the reaction. In practice, one often starts from alkyl chlorides (X = Cl) and phosphorus compounds with ethoxy groups (−O − R = −O − C 2 H 5 ), so that the very volatile chloroethane is formed as a by-product (R − X) .
Depending on the type of Y and Z, different products are obtained:
- Michaelis-Arbusow products
With Y and / or Z = −S − R the sulfur analogues are obtained. An example is parathion . This reaction is generally used for the production of insecticides and nerve warfare agents ( sarin ; tabun ) prohibited by the Geneva Conventions . The chemistry of phosphoric acid esters was decisively shaped by Gerhard Schrader .
In addition, this reaction is a method of obtaining reagents for the Horner-Wadsworth-Emmons reaction .
Individual evidence
- ^ László Kürti , Barbara Czako: Strategic Applications of Named Reactions in Organic Synthesis. 2nd Edition. Elsevier Academic Press, Amsterdam 2005, ISBN 0-12-369483-3 , p. 16.
literature
- Heinz G. Becker u. a. (Ed.): Organikum . Organic-chemical basic internship . Wiley-VCH, Weinheim 2004, ISBN 3-527-31148-3 .
