1H-1,2,3-Triazole

Triazoles are a family of five-membered rings that contain three nitrogen atoms and two double bonds. The four triazole isomers (1H-1,2,3-, 2H-1,2,3-, 1H-1,2,4-, and 2H-1,2,4-) differ by the arrangement of the nitrogen atoms and the locations of their three hydrogen atoms. All of the triazoles are planar and aromatic.

1H-1,2,3-Triazole, like all triazoles, is highly soluble in water. In aqueous solution it tautomerizes to its 2H-isomer with a 1H/2H ratio of ≈1:2. Both isomers have essentially the same melting and boiling points, making them very difficult to separate from each other.

In 1910, German chemists Otto Dimroth* and Gustav Fester synthesized 1H-1,2,3-triazole by heating a solution of hydrazoic acid (HN₃) and acetylene at 100 ºC for 70 h. Sodium azide can be used in place of HN₃ if the solution is acidified. Dimroth is best known for his discovery of the eponymous rearrangement of amine-substituted 1,2,3-triazoles, in which the substituent nitrogen atom and its nearest ring nitrogen atom exchange places.

The 1,2,3-triazole moiety is considered to be a pharmacophore in that it can interact with specific biological targets. It is a component of such pharmaceuticals as the cephalosporin antibiotic cefatrizine; tazobactam, which broadens the spectrum of certain antibiotics; and carboxyamidotriazole, a calcium channel blocker that may be useful to combat cancer.