3,4-Di­hydroxy­phenyl­acetic acid

In the title compound, C₈H₈O₄, the acetic acid side chain adopts a roughly perpendicular orientation with respect to the phenyl ring. Hydro­gen bonding between carboxyl groups results in the formation of a centrosymmetric dimer. An intramolecular hydrogen bond is formed in the catechol part of the mol­ecule. Molecules are linked together through hydrogen bonds between hydroxyl and carboxyl­ic acid O atoms.