Skraup reaction
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The Skraup synthesis is a chemical reaction used to synthesize quinolines. It is named after the Czech chemist Zdenko Hans Skraup (1850-1910). In the archetypal Skraup, aniline is heated with sulphuric acid, glycerol, and an oxidizing agent, like Nitrobenzene to yield quinoline. [1][2][3][4]

The Skraup reaction

In this example, nitrobenzene serves as both the solvent and the oxidizing agent. The reaction, which otherwise has a reputation for being violent, is typically conducted in the presence of ferrous sulfate.[5]Arsenic acid may be used instead of Nitrobenzene and the former is better since the reaction is less violent.[6]

Reaction mechanism

The mechanism is unclear, yet there is good reason to believe that acrolein or acraldehyde (obtained by dehydration of glycerol in presence of concentrated sulphuric acid) is an intermediate, which then undergoes 1,4-addition. Acraldehyde itself is not used since it undergoes polymerisations under the conditions of the experiment.[6]

References

  1. ^  Skraup, Z. H. "Eine Synthese des Chinolins" Berichte 1880, 13, 2086-7.
  2. ^  Manske, R. H. F. Chem. Rev. 1942, 30, 113. (Review)
  3. ^  Manske, R. H. F.; Kulka, M. Org. React. 1953, 7, 80-99. (Review)
  4. ^  Wahren, M. Tetrahedron 1964, 20, 2773. (Review)
  5. ^  Clarke, H. T.; Davis, A. W. “Quinoline” Organic Syntheses Collective Volume 1, page 478 (1941). http://www.orgsyn.org/orgsyn/pdfs/CV1P0478.pdf.
  6. ^  Finar, I. L.; "Organic Chemistry" Volume 1, page 857 (1973)

See also

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