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any of several six-membered heterocyclic compounds containing three nitrogen atoms in the ring. The substituted triazines, which are the best known, exist in all three possible systems: vicinal 1,2,3-triazines (I), asymmetric 1,2,4-triazines (II), and symmetric 1,3,5-triazines (III).
Triazines are strong bases, which yield salts with acids. Substituted 1,3,5-triazines, which are used as herbicides (for example, atrazine, desmetryn, and prometryn) and dyes and in the production of plastics and rubbers, have the greatest practical importance. They are obtained, for example, from cyanuric chloride (1) or by the trimerization of the nitriles of carboxylic acids (2):