Cyanuric chloride is an organic compound with the formula (NCCl)3. This white solid is the chlorinated derivative of 1,3,5-triazine. It is the trimer of cyanogen chloride. Cyanuric chloride is the main precursor to the popular but controversial herbicide atrazine.

Production

Cyanuric chloride is prepared in two steps from hydrogen cyanide via the intermediacy of cyanogen chloride, which is trimerized at elevated temperatures over a carbon catalyst: In 2005, approximately 200,000 tons were produced.

Industrial uses

It is estimated that 70% of cyanuric chloride is used in the preparation of the triazine-class pesticides, especially atrazine. Such reactions rely on the easy displacement of the chloride with nucleophiles such as amines: Other triazine herbicides, such as simazine, anilazine and cyromazine are made in an analogous way. Cyanuric chloride is also used as a precursor to dyes and crosslinking agents. The largest class of these dyes are the sulfonated triazine-stilbene optical brighteners (OBA) or fluorescent whitening agents (FWA) commonly found in detergent formulas and white paper. Many reactive dyes also incorporate a triazine ring. They are also manufactured by way of the chloride displacement reaction shown above.

Reactivity

The chloride centers are easily replaced. Amines give melamine derivatives, for example in the synthesis of dendrimers: It reacts with hydrosulfide to give thiocyanuric acid ((S\dCNH)3).

Organic synthesis

Cyanuric chloride is employed as a reagent in organic synthesis for the conversion of alcohols into alkyl chlorides, and carboxylic acids into acyl chlorides: It is also used as a dehydrating agent, e.g. in the conversion of amides to nitriles, and for the activation of carboxylic acids for reduction to alcohols. Heating with DMF gives "Gold's reagent" Me2NCH=NCH=NMe2+Cl−, which is a versatile source of aminoalkylations and a precursor to heterocycles. Cyanuric chloride can also be used as an alternative to oxalyl chloride in the Swern oxidation.