Terephthalaldehyde

Terephthalaldehyde is an off-white to white needle-like crystalline powder, with a water solubility of about 3 g/L at 50 °C, readily soluble in ethanol, ether and hot water — an important downstream fine chemical of p-xylene. Each end of the molecule carries an active aldehyde group, giving it a dual character as monomer and intermediate.

The two aldehyde groups independently undergo nucleophilic addition, condensation (Schiff bases with amines; Knoevenagel condensation with active methylene compounds), oxidation (to terephthalic acid) and reduction (to p-xylylene glycol); they can also build bis-heterocyclic structures with bis-nucleophiles, making it a core raw material for linear polymer monomers, bifunctional ligands and symmetric drugs.