Dinicotinic acid (pyridine-3,5-dicarboxylic acid) is a heterocyclic organic compound, more precisely a heteroaromatic. It is one of many pyridinedicarboxylic acids and consists of a pyridine ring carrying to carboxy groups in the 3- and 5-positions.
Dinicotinic acid can be formed by heating pyridine-2,3,5,6-tetracarboxylic acid or carbodinicotinic acid (pyridine-2,3,5-tricarboxylic acid).
The acid is sparingly soluble in water and ether. Its melting point of 323 ðC is the highest among pyridinedicarboxylic acids. Upon heating, it decarboxylates and decomposes to nicotinic acid: