Gallic acid is an organic acid, also known as 3,4,5-trihydroxybenzoic acid, found in gallnuts , sumac, witch hazel, tea leaves, oak bark, and other plants. The chemical formula is C6H2(OH)3CO2H. Gallic acid is found both free and as part of tannins.
The COOH group has a pKa of 4.5, and the phenolic OHs have pKa 10.
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