Étard reaction

Source: Wikipedia, the free encyclopedia.

The Étard reaction is a

methyl group to an aldehyde using chromyl chloride.[1][2][3] For example, toluene can be oxidized to benzaldehyde
.

It is named for the French chemist

Alexandre Léon Étard (5 January 1852, Alençon
– 1 May 1910).

Reaction mechanism

The reaction mechanism proceeds via an

sodium sulphite. Typical solvents for the reaction include carbon disulfide, dichloromethane,[4] chloroform, and carbon tetrachloride, with carbon tetrachloride being the most common. To obtain a highly purified aldehyde product, the Étard complex precipitate is often purified before decomposition in order to prevent reaction with any unreacted reagent. The reaction is normally carried out for a few days to several weeks and the yields are high.[5][6]

The Etard reaction
The Etard reaction

Limitations

The Étard reaction is most commonly used as a relatively easy method of converting

benzyl methyl ketone, and several chlorinated products, with benzyl methyl ketone being the major product.[7][8] Another example arises from the Étard reaction of trans-decalin which results in a mixture of trans-9-decalol, spiro [4.5]decan-6-one, trans-1-decalone, cis-1-decalone, 9,10-octal-1-one, and 1-tetralone.[9]

Other oxidation reagents like potassium permanganate or potassium dichromate oxidize to the more stable carboxylic acids.

Uses

Oxidation of toluene to benzaldehyde is quite a useful conversion. Benzaldehyde is routinely used for its almond flavor. The aldehyde is comparatively reactive and readily participates in aldol condensations. Benzaldehyde can serve as a precursor for various compounds, including dyes, perfumes, and pharmaceuticals. For example, the first step in the synthesis of ephedrine is condensation of benzaldehyde with nitroethane [citation needed]. Additionally, benzaldehyde is instrumental in the synthesis of phentermine.[10] Unlike other oxidising agents (like KMnO4 or CrO3 etc.), chromyl chloride does not oxidise aldehyde to carboxylic acid.

References

  1. ^ Étard, A. (1880). "Sur la synthèse desaldéhydes aromatiques; essence de cumin" [On the synthesis of aromatic aldehydes ; essence of cumin]. Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences (in French). 90: 534. Archived from the original on 1 March 2012.
  2. ^ Étard, A. (1881). "Recherches sur le rôle oxydant de l'acide chlorochromique". Annales de Chimie et de Physique (in French). 22: 218–286. Archived from the original on 1 March 2012.
  3. ^ Hartford, W. H. & Darrin, M. (1958). "The Chemistry Of Chromyl Compounds".
    doi:10.1021/cr50019a001
    .
  4. ISBN 0471936235
    .
  5. doi:10.1016/s0040-4020(01)98572-2
    .
  6. doi:10.1139/v58-093
    .
  7. doi:10.1016/s0040-4020(01)92538-4
    .
  8. doi:10.1016/s0040-4039(00)70878-1
    .
  9. doi:10.1016/s0040-4020(01)98663-6
    .
  10. ISBN 978-0-444-52166-8
    .
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