34dihydroxybenzoic

3,4-Dihydroxybenzoic acid, also known as protocatechuic acid, is a dihydroxybenzoic acid with hydroxyl groups at the 3 and 4 positions on the benzene ring and a carboxylic acid substituent. Its chemical formula is C7H6O4 and its molar mass is about 154.12 g/mol. The molecule typically appears as a white to pale crystalline solid and is soluble to a limited extent in water, with greater solubility in alkaline solutions due to deprotonation of the carboxyl group and phenolic OH groups.

Chemical properties and structure: the compound features a benzoic acid core with two adjacent hydroxyl substituents, giving it a catechol-like moiety. The carboxyl group provides acidity (pKa around 4), while the phenolic OH groups are weakly acidic (pKa values typically in the high 9s to around 10). The combination of a carboxyl group and adjacent hydroxyls influences its chemical reactivity, including antioxidant behavior.

Occurrence and uses: protocatechuic acid is widely distributed in nature and occurs in many plants, including fruits, vegetables, and beverages such as tea and wine. It is produced in plants as a metabolic intermediate during the degradation of polyphenols and lignin. In industry and research, it is used as an intermediate in the synthesis of dyes, polymers, and pharmaceuticals, and it is studied for antioxidant, anti-inflammatory, antimicrobial, and neuroprotective activities.

Safety and handling: protocatechuic acid is generally handled as a chemical reagent and is used under standard laboratory safety practices. It is advisable to consult material safety data when handling concentrated forms.