What Is Cyanuric Acid?
Cyanuric Acid is an organic compound synthesized from urea. It is a colorless crystalline solid at room temperature and pressure. Its chemical formula is C3H3O3N3. Its molar mass is 129.1 g/mol, melting point is 320 to 360°C, and CAS number is 108-80-5.
Since it has a trione structure with three carbonyl groups, it is in equilibrium between two structures: a keto form and an enol form. The enol form is called cyanuric acid and the keto form is called isocyanuric acid.
Properties of Cyanuric Acid
Cyanuric acid is a tri-polymerized molecule of urea.
By heating urea to approximately 200°C, a mixture of cyanuric acid with ammeline and ammelides is obtained. By adding inorganic strong acids such as hydrochloric acid and sulfuric acid, other substances are converted to isocyanuric acid, resulting in highly pure isocyanuric acid.
Cyanuric acid is virtually insoluble in water and acetone, and soluble in small amounts in organic solvents such as ether and alcohol. It is also highly soluble in pyridine and hot water.
Uses of Cyanuric Acid
Cyanuric acid is rarely used on its own, but is converted to derivatives before being used. Among isocyanuric acid derivatives, trichloroisocyanuric acid (chlorinated isocyanuric acid) and melamine cyanurate are industrially used.
1. Chlorinated Isocyanuric Acid
Chlorinated isocyanuric acid is a substance obtained by replacing several hydrogen atoms of isocyanuric acid with chlorine atoms. The name trichloroisocyanuric acid refers to the three substitutions, while dichloroisocyanuric acid refers to the two substitutions.
Chlorinated cyanuric acid is a white crystalline solid with a strong chlorine odor. It is often used in the form of sodium or potassium salts to increase water solubility.
Comparing trichloroisocyanuric acid and dichloroisocyanuric acid, trichlorocyanuric acid is less soluble in water, and comparing sodium salt and potassium salt, potassium salt is less soluble. Therefore, it is important to select the appropriate compound for the application.
When in contact with water, they quickly decompose into hypochlorous acid and cyanuric acid. Hypochlorous acid is a powerful oxidizing agent and has bactericidal properties. For this reason, it has been used primarily as a disinfectant to disinfect water in swimming pools, or as a detergent or bleaching agent. Compared to inorganic water treatment agents, chlorine has the characteristic of dissolving slowly over a long period of time.
It is considered less toxic because it does not accumulate in the tissues of the human body and is excreted quickly. However, care must be taken when storing it because it can decompose to produce toxic gases such as hydrogen chloride, hypochlorous acid, and nitrogen oxide.
Applications other than disinfectants include chlorinating agents in organic chemistry experiments and anti-frizz agents for wool.
2. Melamine Cyanurate
Melamine cyanurate is a substance obtained by the reaction of cyanuric acid with melamine. Melanin and cyanuric acid form salts via hydrogen bonds only, and no covalent bonds are formed between them. It is insoluble in water, but is easily dispersed in organic solvents. It is a crystalline white solid at room temperature and pressure, and is used as a white solid lubricant.
In addition, a carbon foam layer is formed during the thermal decomposition process, and this layer is seen to work as a heat and oxygen barrier. Since it does not contain halogens, produces almost no smoke during decomposition, and emits only low-toxicity gases such as nitrogen, carbon dioxide, and ammonia, it is attracting attention as an environmentally friendly flame retardant. It should be stored in a dry environment at room temperature.