Cyanuric chloride is the chemical compound with the formula (NCCl)₃. This colorless solid is the chlorinated derivative of 1,3,5-triazine. It is the trimer of cyanogen chloride ^[1].

Cyanuric acid is prepared in two steps from hydrogen cyanide via the intermediacy of cyanogen chloride, which is trimerized at elevated temperatures over a carbon catalyst:

HCN + Cl2 ? ClCN + HCl

3 ClCN ? (ClCN)₃

In 2005, approximately 200M kg were produced.^[2]

Precursor to pesticides

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:

(ClCN)₃ + RNH₂ ? (RNHCN)(ClCN)₂ + RNH₃⁺Cl^-

Cyanuric chloride is 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.^[2]

Organic synthesis

In one specialized application, cyanuric chloride is employed as a reagent in organic synthesis for the conversion of alcohols and carboxylic acids into alkyl and acyl chlorides, respectively. It is also used as a dehydrating agent 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.^[3]

The chlorine atoms are easily replaced by amines to a melamine for example in the synthesis of this first generation dendrimer ^{[4] [5]}:

Cyanuric chloride based dendrimer

or in the synthesis of an experimental adenosine receptor ligand ^[6]:

Example use cyanuric chloride in pharma WO 03101980 patent

References

1. ↑ Cyanuric chloride at Chemicalland21.com
2. ↑ ^{a b} Klaus Huthmacher, Dieter Most "Cyanuric Acid and Cyanuric Chloride" Ullmann's Encyclopedia of Industrial Chemistry" 2005, Wiley-VCH, Weinheim. ISBN 10.1002/14356007.a08 191
3. ↑ Probst, D. A.; Hanson, P. R.; Barda, D. A. "Cyanuric Chloride" in Encyclopedia of Reagents for Organic Synthesis, 2004, John Wiley & Sons.
4. ↑ Kilogram-Scale Synthesis of a Second-Generation Dendrimer Based on 1,3,5-Triazine Using Green and Industrially Compatible Methods with a Single Chromatographic Step Abdellatif Chouai and Eric E. Simanek J. Org. Chem. 2008, 73, 2357-2366
5. ↑ Reagent: DIPEA, amine protective group: BOC
6. ↑ (Reagent number two: norephedrine, base DIPEA)

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