Oxalic acid is an organic compound with the formula C₂H₂O₄. Oxalic acid is an organic compound with the formula C2H2O4. Oxalic acid | (COOH)2 or HOOCCOOH or C2H2O4 | CID 971 - structure, chemical names, physical and chemical properties, classification, patents, literature,. What is Oxalate? Oxalic acid is an organic compound found in many plants. Oxalic acid, a colorless, crystalline, toxic organic compound belonging to the family of carboxylic acids. Oxalic acid, naturally occurs in many plants (spinach, ginger, chocolate, etc.