Pool Chemicals & Testing

Cyanuric acid or 1,3,5-triazine-2,4,6-triol is an chemical compound with the formula (CNOH)₃. Like many industrially useful chemicals, this triazine has many synonyms. This white solid is the cyclic trimer of cyanic acid, HOCN. more...

It finds use as a precursor or a component of bleach, disinfectants, and herbicides.

Chemical and properties

Cyanuric acid is odorless, hygroscopic, and commonly used as a crystalline powder. On heating above 320 °C, the solid decomposes to toxic nitrogen oxides and cyanic acid.

The two chemical structures shown in the infobox readily interconvert: they are tautomers. The triol tautomer has aromatic character. Consequently, the hydroxyl (-OH) groups assume phenolic character, becoming more acidic than hydroxyl groups in typical alcohols. Deprotonation with base affords a cyanurate salt.

Synthesis

Cyanuric acid (CYA) was first synthesized by Wöhler in 1829 by the thermal decomposition of urea and uric acid. The current industrial route to CYA entails the thermal decomposition of urea (thermal decomposition). The production of CYA and ammelide commence simultaneously at approximately 175 °C, in the following two reactions involving both biuret and isocyanic acid as intermediates:

H₂N-CO-NH-CO-NH₂(m) + HNCO(g) → CYA(s) + NH₃(g)

H₂N-CO-NH-CO-NH₂(m) + HNCO(g) → ammelide(s) + H₂O(g)

As temperature exceeds 190 °C, other reactions begin to dominate the process.

The first appearance of ammeline occurs prior to 225 °C and is suspected also to occur from decomposition of biuret but is produced at a slower rate than that of CYA or ammelide, by the following reaction:

Read more at Wikipedia.org