Methylisothiazolinone

Key takeaways

Methylisothiazolinone belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Methylisothiazolinone to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Methylisothiazolinone from memory before moving on to harder problems.

Reference excerpt

Methylisothiazolinone (), MIT, or MI, is the organic compound with the formula S(CH)2C(O)NCH3. It is a white solid. Isothiazolinones, a class of heterocycles, are used as biocides in numerous personal care products and other industrial applications. MIT and related compounds have attracted much attention for their allergenic properties, e.g. contact dermatitis.

Chemistry It is prepared by cyclization of cis-N-methyl-3-thiocyanoacrylamide:

NCSCH=CHC(O)NHCH3 → SCH=CHC(O)NCH3 + HCN The crystal and molecular structure of methylisothiazolinone, as determined by in situ cryocrystallography, was reported for the first time in 2024.

Applications

Methylisothiazolinone is used for controlling microbial growth in water-containing solutions. It is typically used in a formulation with 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT), in a 3:1 mixture (CMIT:MIT) sold commercially as Kathon. Kathon is supplied to manufacturers as a concentrated stock solution containing from 1.5 to 15% of CMIT/MIT. Kathon also has been used to control slime in the manufacture of paper products that contact food. In addition, this product serves as an antimicrobial agent in latex adhesives and in paper coatings that also contact food.

Hazards MIT is allergenic and cytotoxic, and this has led to some concern over its use. A report released by the European Scientific Committee on Cosmetic Products and Non-food Products Intended for Consumers (SCCNFP) in 2003 also concluded that insufficient information was available to allow for an adequate risk assessment analysis of MIT. Rising reports of consumer impact led to new research, including a report released in 2014 by the European Commission Scientific Committee on Consumer Safety which reported:

The dramatic rise in the rates of reported cases of contact allergy to MI, as detected by diagnostic patch tests, is unprecedented in Europe; there have been repeated warnings about the rise. The increase is primarily caused by increasing consumer exposure to MI from cosmetic products; exposures to MI in household products, paints and in the occupational setting also need to be considered. The delay in re-evaluation of the safety of MI in cosmetic products is of concern to the SCCS; it has adversely affected consumer safety. The American Contact Dermatitis Society named methylisothiazolinone "contact allergen of the year" in 2013. The North American Contact Dermatitis Group found that methylisothiazolinone caused 10.9% positive reactions, being the third most common contact allergen in patch test results which surveyed close to 5000 contact dermatitis patients. Additionally, new research into cross reactivity of MIT-sensitized patients to variants benzisothiazolinone and octylisothiazolinone have found that reactions may occur if present in sufficient amounts. In the United States, the Environmental Protection Agency has a 1998 data sheet on methylisothiazolinone in their Pesticides section which reads in part "Human Health Assessment: Toxicity: In studies using laboratory animals, methylisothiazolinone has been shown to be of moderate acute toxicity by the oral and inhalation routes. It is highly acutely toxic when applied dermally or to the eye and is considered to be corrosive."

Regulation In 2014, the European Commission Scientific Committee on Consumer Safety further issued a voluntary ban on the MCI/MI mixture from leave-on products such as body creams. The measure applied for products placed on the market after 16 July 2015." Shortly thereafter, Canada moved to adopt similar measures in its Cosmetic Ingredients Hotlist. Based on the opinion of the Scientific Committee on Consumer Safety (SCCS) of 2013, Commission Regulation (EU) 2016/1198 of 22 July 2016 amending Annex V to Regulation (EC) No 1223/2009 of the European Parliament and of the council on cosmetic products banned the use of methylisothiazolinone in leave-on products (skin creams and lotions) effective 12 February 2017 and limited it to 0.01% in rinse-off products (e.g. shampoo). Effective 27 January 2018 (placing on the market), the maximum concentration in rinse-off products was reduced to 0.0015%.

References

External links CMIT/MIT Assessment 2014 EPA Re-registration Review Docket with Public Commentary Reregistration Eligibility Decision of MIT by US EPA Methylisothiazoline in the Consumer Product Information Database Material Safety Data Sheet for product containing 0.1-1% MIT Commission Scientific Committee on Consumer Safety Opinion on Methylisothiazolinone (P94) Submission II (Sensitization only) SCCS/1521/13 Methylisothiazolinone at the National Library of Medicine 2014 EPA Re-registration Review Docket with Public Commentary

Illustrations

Worked examples

Example 1 — a first encounter with Methylisothiazolinone

Start with the simplest possible case. Write down what Methylisothiazolinone claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Methylisothiazolinone before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Methylisothiazolinone ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Methylisothiazolinone

In research: Methylisothiazolinone appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Methylisothiazolinone in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Methylisothiazolinone is common in secondary-school and first-year university syllabi. It links to neighbouring topics Isothiazolinones, Methyl compounds, Preservatives, so understanding it makes those chapters shorter.
In everyday life: Look for Methylisothiazolinone outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Methylisothiazolinone in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Methylisothiazolinone means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Methylisothiazolinone out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Methylisothiazolinone in simple terms?

Methylisothiazolinone (), MIT, or MI, is the organic compound with the formula S(CH)2C(O)NCH3. It is a white solid.

Why does Methylisothiazolinone matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Methylisothiazolinone?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Methylisothiazolinone.