Salicylaldehyde

Salicylaldehyde
Names
Preferred IUPAC name
2-Hydroxybenzaldehyde
Other names
Salicylaldehyde (no longer recommended[1])
Salicylic aldehyde
o-Hydroxybenzaldehyde
Identifiers
90-02-8 YesY
3D model (Jmol) Interactive image
ChEBI CHEBI:16008 YesY
ChEMBL ChEMBL108925 YesY
ChemSpider 13863618 YesY
ECHA InfoCard 100.001.783
UNII 17K64GZH20 YesY
Properties
C7H6O2
Molar mass 122.12 g/mol
Density 1.146 g/cm3
Melting point −7 °C (19 °F; 266 K)
Boiling point 196 to 197 °C (385 to 387 °F; 469 to 470 K)
Related compounds
Related compounds
 Salicylic acid
Benzaldehyde
Salicylaldoxime
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Salicylaldehyde (2-hydroxybenzaldehyde) is the organic compound with the formula C6H4CHO-2-OH.[2] Along with 3-hydroxybenzaldehyde and 4-hydroxybenzaldehyde, it is one of the three isomers of hydroxybenzaldehyde. This colorless oily liquid has a bitter almond odor at higher concentration. Salicylaldehyde is a key precursor to a variety chelating agents, some of which are commercially important.

Production

Salicylaldehyde is prepared from phenol and chloroform by heating with sodium hydroxide or potassium hydroxide in a Reimer–Tiemann reaction:[3]

Alternatively, it is produced by condensation of phenol or its derivatives with formaldehyde to give hydroxybenzyl alcohol, which is oxidized to the aldehyde.

Salicylaldehydes in general may be prepared from the corresponding phenol by the Duff reaction, or by treatment with paraformaldehyde in the presence of magnesium chloride and a base.[4]

Natural occurrences

Salicylaldehyde was identified as a characteristic aroma component of buckwheat.[5]

It is also one of the components of castoreum, the exudate from the castor sacs of the mature North American beaver (Castor canadensis) and the European beaver (Castor fiber), used in perfumery.

Furthermore, salicylaldehyde occurs in the larval defensive secretions of several leaf beetle species that belong the subtribe Chrysomelina.[6] An example for a leaf beetle species that produces salicylaldehyde is the red poplar leaf beetle Chrysomela populi.

Reactions and applications

Salicylaldehyde is used to make the following:

Catechol, benzofuran, a salicylaldehydimine (R = alkyl or aryl), 3-carbethoxycoumarin.
  1. Oxidation with hydrogen peroxide gives catechol (1,2-dihydroxybenzene) (Dakin reaction).[7]
  2. Etherification with chloroacetic acid followed by cyclisation gives the heterocycle benzofuran (coumarone).[8] {The first step in this reaction to the substituted benzofuran is called the Rap–Stoermer condensation after E. Rap (1895) and R. Stoermer (1900).[9][10]}
  3. Salicylaldehyde is converted to chelating ligands by condensation with amines. With ethylenediamine, it condenses to give the ligand salen. Hydroxylamine gives salicylaldoxime.
  4. Condensation with diethyl malonate gives 3-Carbethoxycoumarin (a derivative of coumarin) via an aldol condensation.[11]

References

  1. ↑ Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 652. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  2. ↑ Merck Index, 11th Edition, 8295
  3. ↑ Brühne, F.; Wright, E. (2005), "Benzaldehyde", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a03_463
  4. ↑ Trond Vidar Hansen; Lars Skattebøl (2005). "Ortho-Formylation of Phenols; Preparation of 3-Bromosalicylaldehyde". Org. Synth. 82: 64.
  5. ↑ Janeš, D.; Kreft, S. (2008). "Salicylaldehyde is a characteristic aroma component of buckwheat groats". Food Chemistry. 109 (2): 293–298. doi:10.1016/j.foodchem.2007.12.032.
  6. ↑ Pauls, G., Becker, T., et al. (2016). Two Defensive Lines in Juvenile Leaf Beetles; Esters of 3-nitropropionic Acid in the Hemolymph and Aposematic Warning. Journal of Chemical Ecology 42 (3) 240-248.
  7. ↑ Dakin, H. D. (1923). "Catechol" (PDF). Org. Synth. 3: 28.; Coll. Vol., 1, p. 149
  8. ↑ Burgstahler, A. W.; Worden, L. R. (1966). "Coumarone" (PDF). Org. Synth. 46: 28.; Coll. Vol., 5, p. 251
  9. ↑ Rap, E. (November 1895). "Sull' α-Benzoilcumarone" [On the α-Benzoylcoumaron]. Gazzetta Chimica Italiana. 2 (4): 285–290.
  10. ↑ Stoermer, R. (1900). "Synthesen und Abbaureactionen in der Cumaronreihe". Liebig's Annalen der Chemie. 312 (3): 237–336. doi:10.1002/jlac.19003120302.
  11. ↑ Horning, E. C.; Horning, M. G.; Dimmig, D. A. (1948). "3-Carbethoxycoumarin" (PDF). Org. Synth. 28: 24.; Coll. Vol., 3, p. 165
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