2-Methyl-4-Isothiazolin-3-one
[CAS# 2682-20-4]

Identification

• Classification: Analytical chemistry >> Standard >> Cosmetic standard
• Name: 2-Methyl-4-Isothiazolin-3-one
• Synonyms: 2-Methyl-2,3-dihydroisothiazol-3-one; 2-Methyl-3-isothiazolone; 2-Methylisothiazol-3-one; Methyl-3(2H)-isothiazolone
• Molecular Formula: C₄H₅NOS
• Molecular Weight: 115.15
• CAS Registry Number: 2682-20-4
• EC Number: 220-239-6
• SMILES: CN1C(=O)C=CS1

Properties

• Density: 1.25 (14% aq.)

Safety Data

• Hazard Symbols: GHS05;GHS06;GHS09 Danger
• Risk Statements: H330-H311-H301-H314-H318-H317-H400-H410
• Safety Statements: P260-P261-P262-P264-P264+P265-P270-P271-P272-P273-P280-P284-P301+P316-P301+P317-P301+P330+P331-P302+P352-P302+P361+P354-P304+P340-P305+P354+P338-P316-P317-P319-P320-P321-P330-P333+P317-P361+P364-P362+P364-P363-P391-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Skin corrosion	Skin Corr.	1B	H314
Acute toxicity	Acute Tox.	3	H301
Skin sensitization	Skin Sens.	1	H317
Acute toxicity	Acute Tox.	3	H311
Serious eye damage	Eye Dam.	1	H318
Specific target organ toxicity - single exposure	STOT SE	3	H335
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Acute toxicity	Acute Tox.	2	H330
Skin sensitization	Skin Sens.	1A	H317
Acute toxicity	Acute Tox.	3	H331
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	4	H332
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Acute toxicity	Acute Tox.	2	H310
Skin corrosion	Skin Corr.	1	H314
Acute toxicity	Acute Tox.	2	H300
Acute toxicity	Acute Tox.	4	H312
Chronic hazardous to the aquatic environment	Aquatic Chronic	4	H413
Skin corrosion	Skin Corr.	1C	H314
Eye irritation	Eye Irrit.	2	H319
Acute toxicity	Acute Tox.	1	H330
Skin corrosion	Skin Corr.	1A	H314
Acute toxicity	Acute Tox.	1	H310

Discovery and Applications

2-Methyl-4-isothiazolin-3-one (MIT) is a powerful biocide that was discovered in the mid-20th century to meet the growing demand for effective antimicrobial agents across a wide range of industries. The isothiazolinone family of compounds, including MIT, stems from research dedicated to finding solutions to the problem of microbial contamination in industrial and consumer products.

MIT has the molecular formula C4H5NOS, with a methyl-substituted isothiazolinone ring. This structure imparts strong antimicrobial properties, making MIT effective against a wide range of microorganisms, including bacteria, fungi, and algae. MIT works by disrupting microbial cell membranes and inhibiting essential enzymes, resulting in cell death. Due to its high efficacy, it is typically used in low concentrations.

One of the main applications of MIT is as a preservative for industrial products. It is widely used in paints, adhesives, and coatings to prevent the growth of microorganisms that can cause spoilage and degradation. The addition of MIT ensures the longevity and stability of these products, maintaining their quality during storage and use.

MIT is also used in personal care and cosmetics, such as shampoos, conditioners, and lotions. As a preservative, MIT prevents microbial contamination, extends shelf life, and ensures that these products are safe for consumers. Due to its powerful biocidal properties, only small amounts of MIT are needed to achieve effective preservation.

In household cleaning products and disinfectants, MIT helps ensure that these formulations are effective in eliminating bacteria and other pathogens on surfaces. This application enhances the antimicrobial properties of cleaners, helping to create a hygienic living environment.

MIT is used in water treatment systems to control microbial growth in cooling towers, pulp and paper mills, and during oil extraction. Its effectiveness against a wide range of microorganisms makes it valuable in maintaining water quality and preventing biofouling, which can lead to operational inefficiencies and equipment damage.

In the textile and leather industries, MIT is used to prevent microbial degradation during manufacturing and storage. This use helps maintain the integrity and appearance of fabrics and leather products, ensuring that they do not mold or mildew.

While MIT is highly effective as a biocide, its use is regulated due to the health risks that exposure can pose. Regulatory agencies, such as the Environmental Protection Agency (EPA) and the European Chemicals Agency (ECHA), have established guidelines for safe concentrations of MIT in various applications. Proper handling and use are essential to minimize adverse effects on human health and the environment.

References

2024. Insight into the photodegradation of methylisothiazolinone and benzoisothiazolinone in aquatic environments. Water Research, 265.
DOI: 10.1016/j.watres.2024.122301

2024. Current frequency of contact allergy to isothiazolinones (methyl-, benz- and octylisothiazolinone) across Europe. Contact Dermatitis, 91(2).
DOI: 10.1111/cod.14641

2023. Synergy between UV light and trichloroisocyanuric acid on methylisothiazolinone degradation: Performance, kinetics and degradation pathway. Environmental Research, 236.
DOI: 10.1016/j.envres.2023.116693