|Jmol-3D images||Image 1|
|Molar mass||122.12 g/mol|
|Melting point||−7 °C (19 °F; 266 K)|
|Boiling point||196–197 °C|
|Related compounds||Salicylic acid
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
Salicylaldehyde (2-hydroxybenzaldehyde) is the organic compound with the formula C6H4CHO-2-OH. 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.
Alternative, it is produced by condensation of phenol or its derivatives with formaldehyde to give hydroxybenzyl alcohol, which is oxidized to the aldehyde.
Reactions and applications
Salicylaldehyde is a common highly functionalized arene that has often been exploited as a precursor to still other chemicals, which are shown in the figure, from the left: catechol, benzofuran, a salicylaldehydimine (R = alkyl or aryl), 3-carbethoxycoumarin.
Salicylaldehyde is converted to chelating ligands by condensation with amines. With ethylenediamine, it condenses to give the ligand salen. Hydroxylamine gives salicylaldoxime. Oxidation with hydrogen peroxide gives catechol (1,2-dihydroxybenzene) (Dakin reaction). Condensation with diethyl malonate gives a derivative of the heterocycle coumarin via an aldol condensation. Etherification with chloroacetic acid followed by cyclisation gives the heterocycle benzofuran. The first step in this reaction to the substituted benzofuran is called the Rap–Stoermer condensation after E. Rap (1895) and R. Stoermer (1900).
- Merck Index, 11th Edition, 8295
- Brühne, F.; Wright, E. (2005), "Benzaldehyde", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a03_463
- Trond Vidar Hansen; Lars Skattebøl (2005), "Ortho-Formylation of Phenols; Preparation of 3-Bromosalicylaldehyde", Org. Synth. 82: 64
- 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.
- Dakin, H. D. (1923), "Catechol", Org. Synth. 3: 28; Coll. Vol. 1: 149
- Horning, E. C.; Horning, M. G.; Dimmig, D. A. (1948), "3-Carbethoxycoumarin", Org. Synth. 28: 24; Coll. Vol. 3: 165
- Burgstahler, A. W.; Worden, L. R. (1966), "Coumarone", Org. Synth. 46: 28; Coll. Vol. 5: 251
- 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.