Isonipecotic acid is an organic compound that belongs to the class of compounds known as carboxylic acids. It is a dicarboxylic acid with the chemical formula C6H4(CO2H)2. It is a colorless solid that is slightly soluble in water and has a sour taste. It is used in some industrial processes and as an intermediate in the production of other compounds. It is also used as a food additive and as a preservative.