chemistry

Methylchloroisothiazolinone

Methylchloroisothiazolinone is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Methylchloroisothiazolinone rather than just read about it. In short: Methylchloroisothiazolinone, also referred to as MCI, is the organic compound with the formula S(C2HCl)C(O)N(CH3). It is a white solid that melts near room temperature.

Key takeaways

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

Reference excerpt

Methylchloroisothiazolinone, also referred to as MCI, is the organic compound with the formula S(C2HCl)C(O)N(CH3). It is a white solid that melts near room temperature. The compound is an isothiazolinone, a class of heterocycles used as biocides. These compounds have an active sulphur moiety that is able to oxidize thiol-containing residues, thereby effectively killing most aerobic and anaerobic bacteria. MCI is often used in combination with methylisothiazolinone, a mixture known as Kathon. The isothiazolinones have attracted attention because they can cause contact dermatitis. Methylchloroisothiazolinone is effective against gram-positive and gram-negative bacteria, yeast, and fungi.

Application Methylchloroisothiazolinone is found in many water-based personal care products and cosmetics. Methylchloroisothiazolinone was first used in cosmetics in the 1970s. It is also used in glue production, detergents, paints, fuels, and other industrial processes. Methylchloroisothiazolinone is known by the registered tradename Kathon CG when used in combination with methylisothiazolinone. Methylchloroisothiazolinone may be used in combination with other preservatives including ethylparaben, benzalkonium chloride, bronopol, and phenoxyethanol.

Hazards Methylchloroisothiazolinone can cause allergic reactions in some people. The first publication of the preservative as a contact allergen was in 1988. Cases of photoaggravated allergic contact dermatitis, i.e. worsening of skin lesions after sun exposure, have also been reported. In pure form or in high concentrations, methylchloroisothiazolinone is a skin and membrane irritant and causes chemical burns. In the United States, maximum authorized concentrations are 15 ppm in rinse-offs (of a mixture in the ratio 3:1 of 5-chloro-2-methylisothiazol 3(2H)-one and 2-methylisothiazol-3 (2H)-one). In Canada, methylchloroisothiazolinone may only be used in rinse-off products in combination with methylisothiazolinone, the total concentration of the combination may not exceed 15 ppm. In the European Union, methylchloroisothiazolinone is permitted only as part of the MCI/MI preservative mixture under Annex V (entry 39) of the Cosmetics Regulation (EC) No 1223/2009. The mixture, in a 3:1 ratio of methylchloroisothiazolinone to methylisothiazolinone, is allowed only in rinse-off products at a maximum concentration of 0.0015% (15 ppm). Its use was restricted to rinse-off products by Commission Regulation (EU) No 1003/2014, applicable from 16 July 2015. Methylisothiazolinone is considered safe in the allowed amount in rinse-off products (0.01%) and safe in leave-in products when formulated to be non-sensitizing.

Incidents An overdose of Kathon by aircraft maintenance personnel, using 38 times the correct amount, resulted in damage to both engines of a Titan Airways aircraft in February 2020. After losing both engines in succession, the Airbus A321 made an emergency landing at Gatwick Airport. The maintenance procedures specified the Kathon to be diluted to 100 PPM by volume, but with the aircraft maintenance technician being unfamiliar with the term "PPM" and the term not being defined in the aircraft maintenance manuals, the technician instead used an online calculator to convert PPM to percentages, misinterpreted the answer, and added 30 kg of Kathon to each wing tank, which was over 38 times the required amount. Over the course of the next day, the Kathon progressively caused more and more damage to the engines, finally resulting in an emergency landing.

References

External links CMIT/MIT Assessment Methylchloroisothiazoline in the Consumer Product Information Database Methylchloroisothiazolinone at the National Library of Medicine

Illustrations

Worked examples

Example 1 — a first encounter with Methylchloroisothiazolinone

Start with the simplest possible case. Write down what Methylchloroisothiazolinone 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 Methylchloroisothiazolinone 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 Methylchloroisothiazolinone 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 Methylchloroisothiazolinone

In research: Methylchloroisothiazolinone 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 Methylchloroisothiazolinone 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: Methylchloroisothiazolinone is common in secondary-school and first-year university syllabi. It links to neighbouring topics Chloroarenes, Isothiazolinones, Methyl compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Methylchloroisothiazolinone 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.

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How to study Methylchloroisothiazolinone in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Methylchloroisothiazolinone 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 Methylchloroisothiazolinone out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Methylchloroisothiazolinone in simple terms?

Methylchloroisothiazolinone, also referred to as MCI, is the organic compound with the formula S(C2HCl)C(O)N(CH3). It is a white solid that melts near room temperature.

Why does Methylchloroisothiazolinone 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 Methylchloroisothiazolinone?

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 Methylchloroisothiazolinone.