Wurtz-Fittig synthesis

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The Wurtz-Fittig synthesis is a name reaction in organic chemistry . It is a form of the Wurtz synthesis expanded by Rudolph Fittig (1835–1910) and is used for the synthesis of alkylated aromatics . However, since the yields are mostly low due to side reactions , the Wurtz-Fittig reaction has no particular synthetic significance.

Overview reaction

In the reaction, a haloalkane and a haloaromatic are reacted with an alkali metal in an inert solvent to form an alkylated aromatic .

Overview reaction of the Wurtz-Fittig synthesis

mechanism

The reaction has strong analogies to the Wurtz synthesis. Instead of chloride or bromide, other halides can also be bound.

Possible mechanism of the Wurtz-Fittig synthesis

In a first step, the more reactive alkyl halide compared to the aryl halide is reduced from sodium to carbanion . This can react in a nucleophilic substitution reaction with the aryl halide to form the corresponding alkylated aromatic.

Side reactions

The driving force behind the process is the formation of the sodium halide which precipitates out of the solution , as this has a high lattice enthalpy. The side reactions are diverse and reduce the yields considerably. The following reactions are possible, for example:

Side reaction of the Wurtz-Fittig synthesis
The prerequisite for this is the presence of β-hydrogen in the alkyl chain of the haloalkane 1 . The carbanion 2 has a very strong basicity and accepts a proton of another alkyl halide . This creates alkanes 3 and alkenes 4 .
Side reaction of the Wurtz-Fittig synthesis
Coupling of the carbanion 1 with another haloalkane 2 . This produces further alkanes 3 .
Side reaction of the Wurtz-Fittig synthesis
Reaction of sodium with the aryl halide 1 . The resulting carbanion 2 reacts with another halogen aromatic compound . Here biphenyls 3 minimize the yield of the Wurtz-Fittig synthesis. However, this side reaction usually does not take place, since the coupling of halogen aromatic compounds with one another generally does not succeed due to their lower reactivity .

See also

Individual evidence

  1. ↑ a b Bernhard Tollens , Rudolph Fittig : About the synthesis of the hydrocarbons of the benzene series (p 303) . In: Annals of Chemistry and Pharmacy . tape 131 , no. 3 , 1864, p. 303-323 , doi : 10.1002 / jlac.18641310307 .
  2. ↑ a b Rudolph Fittig, Joseph König: Ueber das Aethyl- und Diethylbenzol (p) . In: Annals of Chemistry and Pharmacy . tape 144 , no. 3 , 1867, p. 277-294 , doi : 10.1002 / jlac.18671440308 .
  3. ^ László Kürti, Barbara Czakó: Strategic Applications of Named Reactions in Organic Synthesis . Elsevier Science & Technology Books, 2005, ISBN 0-12-369483-3 , pp. 498 .
  4. ↑ T. Laue, A. Plagens: Name and catchword reactions of organic chemistry . Teubner Verlag, 2006, ISBN 3-8351-0091-2 , p. 360 .