Salicylic aldehyde (2-hydroxybenzaldehyde) is anorganic compound with the formulaC6H4OH(CHO).[3][4] Along with3-hydroxybenzaldehyde and4-hydroxybenzaldehyde, it is one of the threeisomers ofhydroxybenzaldehyde. This colorless oily liquid has a bitter almond odor at higher concentration. Salicylaldehyde is a precursor to coumarin and a variety ofchelating agents.
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| Names | |||
|---|---|---|---|
| Preferred IUPAC name 2-Hydroxybenzaldehyde[1] | |||
| Other names Salicylaldehyde Salicylic aldehyde o-Hydroxybenzaldehyde | |||
| Identifiers | |||
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3D model (JSmol) | |||
| 471388 | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider |
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| ECHA InfoCard | 100.001.783 | ||
| EC Number |
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| 3273 | |||
| KEGG | |||
| UNII | |||
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| Properties | |||
| C7H6O2 | |||
| Molar mass | 122.123 g·mol−1 | ||
| 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) | ||
| −64.4·10−6 cm3/mol | |||
| Hazards[2] | |||
| GHS labelling: | |||
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| Warning | |||
| H302,H315,H317,H319,H335,H411 | |||
| P280,P305+P351+P338 | |||
| Safety data sheet (SDS) | [2] | ||
| Related compounds | |||
Related compounds | Salicylic acid Benzaldehyde Salicylaldoxime | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Production
editSalicylaldehyde is produced by condensation of phenol with formaldehyde to give hydroxybenzyl alcohol, which is oxidized to the aldehyde.[4]Salicylaldehydes in general are prepared by ortho-selectiveformylation reactions from the corresponding phenol, for instance by theDuff reaction,Reimer–Tiemann reaction, or by treatment withparaformaldehyde in the presence ofmagnesium chloride and a base.[5][6]
Natural occurrences
editSalicylaldehyde is a characteristic aroma component ofbuckwheat.[7] Salicylaldehyde also occurs in the larval defensive secretions of severalleaf beetle species that belong the subtribe Chrysomelina.[8] An example for a leaf beetle species that produces salicylaldehyde is the red poplar leaf beetleChrysomela populi.
Reactions and applications
editSalicylaldehyde is mainly used commercially as a precursor tocoumarin. The conversion entails condensation withacetic anhydride ("Perkin synthesis").[4]
- Oxidation withhydrogen peroxide givescatechol (1,2-dihydroxybenzene) (Dakin reaction).[9]
- Etherification withchloroacetic acid followed by cyclisation gives the heterocyclebenzofuran (coumarone).[10] The first step in this reaction to the substituted benzofuran is called theRap–Stoermer condensation after E. Rap (1895) and R. Stoermer (1900).[11][12]
- Salicylaldehyde is converted tochelatingligands by condensation with amines. Withethylenediamine, it condenses to give the ligandsalen. Hydroxylamine givessalicylaldoxime.
- Condensation withdiethyl malonate gives 3-carbethoxycoumarin (a derivative ofcoumarin) by analdol condensation.[13]
Elbs persulfate oxidation gives gentisaldehyde (2,5-dihydroxybenzaldehyde).[14][15]
Internal hydrogen bonding
editDue to theortho positioning of the hydroxy- and aldehyde groups, an internalhydrogen bond is formed between the groups. The hydroxy group serves here as the hydrogen bond donor, and the aldehyde as hydrogen bond acceptor. This internal hydrogen is not found in the otherhydroxybenzaldehyde isomers. When the aldehyde is reacted with an amine to form an imine, the internal hydrogen bond is even stronger.[16] In addition,tautomerisation further increases the stability of the compound.[17] The internal hydrogen bond also ensures that the aldehyde (or corresponding imine) is held into the same plane, making the whole molecule essentially flat.[18]
References
edit- ^"Front Matter".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.
- ^abSigma-Aldrich Co.,Salicylaldehyde. Retrieved on 2018-05-24.
- ^Merck Index, 11th Edition,8295
- ^abcMaliverney, Christian; Mulhauser, Michel (2000). "Hydroxybenzaldehydes".Kirk-Othmer Encyclopedia of Chemical Technology.doi:10.1002/0471238961.0825041813011209.a01.ISBN 978-0-471-48494-3.
- ^Trond Vidar Hansen; Lars Skattebøl (2005). "Ortho-Formylation of Phenols; Preparation of 3-Bromosalicylaldehyde".Organic Syntheses.82: 64.doi:10.15227/orgsyn.089.0220.
- ^Brühne, F.; Wright, E. "Benzaldehyde".Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH.doi:10.1002/14356007.a03_463.pub2.ISBN 978-3-527-30673-2.
{{cite encyclopedia}}: CS1 maint: multiple names: authors list (link) - ^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.PMID 26003350.
- ^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.
- ^Dakin, H. D. (1923)."Catechol".Organic Syntheses.3: 28.doi:10.15227/orgsyn.003.0028;Collected Volumes, vol. 1, p. 149.
- ^Burgstahler, A. W.; Worden, L. R. (1966). "Coumarone".Organic Syntheses.46: 28.doi:10.15227/orgsyn.046.0028
{{cite journal}}: CS1 maint: multiple names: authors list (link). - ^Rap, E. (November 1895). "Sull' α-Benzoilcumarone" [On the α-Benzoylcoumaron].Gazzetta Chimica Italiana.2 (4):285–290.
- ^Stoermer, R. (1900)."Synthesen und Abbaureactionen in der Cumaronreihe".Liebig's Annalen der Chemie.312 (3):237–336.doi:10.1002/jlac.19003120302.
- ^Horning, E. C.; Horning, M. G.; Dimmig, D. A. (1948). "3-Carbethoxycoumarin".Organic Syntheses.28: 24.doi:10.15227/orgsyn.028.0024
{{cite journal}}: CS1 maint: multiple names: authors list (link). - ^Sethna, Suresh M. (1951-08-01)."The Elbs Persulfate Oxidation".Chemical Reviews.49 (1):91–101.doi:10.1021/cr60152a002.ISSN 0009-2665.
- ^Denmark, Scott E., ed. (2004-04-30).Organic Reactions (1 ed.). Wiley.doi:10.1002/0471264180.or035.02.ISBN 978-0-471-26418-7.
- ^Schoustra, S.K.; Asadi, V.; Zuilhof, H.; Smulders, M.M.J. (2023)."Internal hydrogen bonding of imines to control and enhance the dynamic mechanical properties of covalent adaptable networks".European Polymer Journal.195: 112209.doi:10.1016/j.eurpolymj.2023.112209.
- ^Metzler, C.M.; Cahill, A.; Metzler, D.E. (1980). "Equilibriums and absorption spectra of Schiff bases".J. Am. Chem. Soc.102 (19):6075–6082.doi:10.1021/ja00539a017.
- ^Kandambeth, S.; Shinde, D.B; Panda, M.K.; Lukose, B.; Heine, T.; Banerjee, R. (2013)."Enhancement of Chemical Stability and Crystallinity in Porphyrin-Containing Covalent Organic Frameworks by Intramolecular Hydrogen Bonds".Angew. Chem. Int. Ed.52 (49):13052–13056.doi:10.1002/anie.201306775.