Methylchloroisothiazolinone (MCI), also known as 1,2-benzisothiazolin-3-one, is a chemical compound with the formula C₄H₄NOSCl. It is a heterocyclic organic compound that contains a five-membered ring with one sulfur atom, one oxygen atom, and one nitrogen atom. It is a white or colorless solid with a pungent odor. MCI is a biocide that is used in a wide variety of personal care products, including shampoos, conditioners, body washes, and cosmetics, to inhibit the growth of bacteria and fungi that can cause spoilage and contamination, such as Pseudomonas, Staphylococcus aureus, E. coli, and Aspergillus niger. It is also used as a preservative in industrial products such as paint, paper, and adhesives, as well as in water-based systems like air conditioning units and hot tubs.

Properties of Methylchloroisothiazolinone

- Chemical formula: C₄H₄NOSCl

- Molar mass: 114.58 g/mol

- Physical form: White or colorless solid

- Odor: Pungent

- Melting point: 35–38 °C

- Boiling point: 204–206 °C

- Water solubility: Soluble in water

- pH stability: Stable between pH 3 and 9

- Antimicrobial activity: Broad spectrum of antimicrobial activity against bacteria, fungi, and algae

Uses of Methylchloroisothiazolinone

- Personal care products: MCI is used as a preservative in a wide variety of personal care products, including shampoos, conditioners, body washes, cosmetics, and wet wipes.

- Industrial products: MCI is used as a preservative in industrial products such as paint, paper, adhesives, and water-based systems like air conditioning units and hot tubs.

- Water treatment: MCI is used as a biocide in water treatment applications to control the growth of bacteria and fungi in cooling towers, swimming pools, and spas.

Safety and Toxicity

Methylchloroisothiazolinone is generally considered safe when used in accordance with recommended guidelines. However, it can cause skin irritation, eye irritation, and allergic reactions in some individuals. It is important for manufacturers to follow regulatory requirements and safety guidelines when using MCI in their products to ensure consumer safety.