Salicylaldehyde
IUPAC name	2-Hydroxybenzaldehyde
Other names	Salicylaldehyde Salicylic aldehyde
Identifiers
CAS number	[90-02-8]
SMILES	OC1=C(C=O)C=CC=C1
Properties
Molecular formula	C7H6O2
Molar mass	122.12 g/mol
Density	1.146 g/cm3
Melting point	-7 °C
Boiling point	196-197 °C
Related compounds
Related compounds	Salicylic acid Benzaldehyde Salicylaldoxime
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references

Salicylaldehyde, or 2-hydroxybenzaldehyde, is the chemical compound with the formula C₆H₄CHO-2-OH^[1]. This colourless oily liquid has a bitter almond odor at higher concentration and a characteristic buckwheat aroma at lower concentration. Salycylaldehyde was identified as a characteristic aroma component of buckwheat ^[2] . Salicylaldehyde is a key precursor to a variety chelating agents, some of which are commercially important. It can be prepared from phenol and chloroform by heating with sodium hydroxide in a Reimer-Tiemann reaction.

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 via condensation with amines. With ethylenediamine, it condenses to give the popular diprotic ligand H₂salen. Hydroxylamine gives salicylaldoxime.
• Oxidation with hydrogen peroxide gives catechol (1,2-dihydroxybenzene).^[3]
• Condensation with diethyl malonate gives a derivative of the heterocycle coumarin.^[4]
• Etherification with chloroacetic acid followed by cyclisation gives the heterocycle benzofuran.^[5]

Other hydroxybenzaldehydes

Three isomers exist of hydroxybenzaldehyde with the hydroxyl group in the ortho, meta, or para position.

3-Hydroxybenzaldehyde has been prepared from m-nitrobenzaldehyde in a sequence of nitro group [[organic reduction, diazotisation of the amine and its hydrolysis^[8][9]

References