salicylaldehyde

Salicylaldehyde, also known as 2-hydroxybenzaldehyde, is an aromatic aldehyde with the formula C7H6O2. It features an aldehyde group adjacent to a phenolic hydroxyl group (ortho). The molecule can form intramolecular hydrogen bonds between the OH and the carbonyl, influencing acidity, reactivity, and spectral properties.

Production and occurrence: It is commonly prepared by the Reimer–Tiemann formylation of phenol, followed by hydrolysis, which yields mainly the ortho-formyl phenol. Alternative routes include oxidation of o-hydroxymethyl benzene derivatives. It is used as an industrial intermediate for the synthesis of various chemicals.

Chemical properties: The aldehyde group makes it an electrophile at the carbonyl carbon and susceptible to reactions with nucleophiles such as amines, alcohols, and organometallic reagents. The ortho-hydroxyl enhances reactivity in electrophilic aromatic substitution and enables formation of hydrogen-bonded intramolecular structures. It can undergo oxidation to the corresponding acid and serves as a versatile building block for further transformations.

Applications: Salicylaldehyde is a versatile intermediate in organic synthesis. It is used to prepare Schiff bases and various heterocycles, and serves as an intermediate in the manufacture of dyes, fragrances, and pharmaceuticals. It can be oxidized to salicylic acid or employed to introduce hydroxybenzaldehyde motifs in target molecules.

Safety: It is a hazardous chemical and can irritate skin, eyes, and the respiratory tract. It is flammable and should be handled in a proper fume hood with appropriate protective equipment.

See also: o-hydroxybenzaldehyde; salicylic acid; formylation reactions.