High Quality Content by WIKIPEDIA articles! Pyrimidine is a heterocyclic aromatic organic compound similar to benzene and pyridine, containing two nitrogen atoms at positions 1 and 3 of the six-member ring. It is isomeric with two other forms of diazine: Pyridazine, with the nitrogen atoms in positions 1 and 2; and Pyrazine, with the nitrogen atoms in positions 1 and 4.