chemistry

Methanesulfonic acid

Methanesulfonic acid 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 Methanesulfonic acid rather than just read about it. In short: Methanesulfonic acid (MsOH, MSA) is an organosulfuric, colorless liquid with the molecular formula CH3SO3H and structure H3C−S(=O)2−OH. It is the simplest of the alkylsulfonic acids (R−S(=O)2−OH).

Key takeaways

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

Reference excerpt

Methanesulfonic acid (MsOH, MSA) is an organosulfuric, colorless liquid with the molecular formula CH3SO3H and structure H3C−S(=O)2−OH. It is the simplest of the alkylsulfonic acids (R−S(=O)2−OH). Salts and esters of methanesulfonic acid are known as mesylates (or methanesulfonates, as in ethyl methanesulfonate). It is hygroscopic.

History and synthesis

Early history German chemist Hermann Kolbe discovered MSA between 1842 and 1845 and originally termed it methyl hyposulphuric acid. The discovery stemmed from earlier work by Berzelius and Marcet in 1813, who treated carbon disulfide with moist chlorine and produced a compound they named "sulphite of chloride of carbon". By reacting it with barium hydroxide Kolbe demonstrated it to actually be trichloromethylsulfonyl chloride (CCl3SO2Cl).

2 CCl3SO2Cl + 3 Ba(OH)2 → Ba(CCl3SO3)2 + 3 BaCl2 + 2 H2O From resulting barium trichloromethylsulfonate Kolbe isolated the free acid, which he was then able to sequentially dechlorinate by electrolytically generated atomic hydrogen to ultimately yield MSA.

CCl3SO3H + 3 H → CHCl2SO3H + 2 H + HCl → … → CH3SO3H + 3 HCl Kolbe's research on methanesulfonic and chloroacetic acids was hailed by Berzelius as strong evidence for his theory of copulated compounds, a modification of radical theory to accommodate substitution reactions which posited the combination of organic and inorganic moieties without significantly altering the properties of the latter. Later in the 19th century, the name transitioned to methyl sulphonic acid. Other historical laboratory synthesis routes included oxidizing methanethiol, dimethyl disulfide or methyl thiocyanate with nitric acid.

Industrial production The first commercial production of MSA, developed in the 1940s by Standard Oil of Indiana, was based on oxidation of dimethylsulfide by O2 from air. Although inexpensive, this process suffered from a poor product quality and explosion hazards. Starting from the 1960s, it received a shortened name of mesylic acid after the term for the "mesyl" group coined by Helferich et al. in 1938. In 1967, the Pennwalt Corporation (USA) developed a different process for dimethylsulfide (as a water-based emulsion) oxidation using chlorine, followed by extraction-purification. In 2022 this chlorine-oxidation process was used only by Arkema (France) for making high-purity MSA. This process is not popular on a large scale, because it co-produces large quantities of hydrochloric acid. Between years 1970 and 2000 MSA was used only on a relatively small-scale in niche markets (for example, in the microelectronic and electroplating industries since the 1980s), which was mainly due to its rather high price and limited availability. However, this situation changed around 2003, when BASF launched commercial production of MSA in Ludwigshafen based on a modified version of the aforementioned air oxidation process, oxidising dimethyldisulfide with nitric acid which is then restored using atmospheric oxygen. The former is produced in one step from methanol from syngas, hydrogen and sulfur. An even better (lower-cost and environmentally friendlier) process of making methanesulfonic acid was developed in 2016 by Grillo-Werke AG (Germany). It is based on a direct reaction between methane and oleum at around 50 °C and 100 bar in the presence of a potassium persulfate initiator. Further addition of sulfur trioxide gives methanedisulfonic acid instead. This technology was acquired and commercialized by BASF in 2019.

Applications Since ca. 2000 methanesulfonic acid has been promoted as a replacement for other acids in industrial and laboratory applications. Methanesulfonic acid can dissolve a wide range of metal salts, many of them in significantly higher concentrations than in hydrochloric acid (HCl) or sulfuric acid (H2SO4). It has the following features:

is a strong acid, has a low vapor pressure (see boiling points in the "Properties" inset), is not an oxidant, in contrast to nitric, sulfuric or perchloric acids. is a liquid at room temperature (The closely related p-toluenesulfonic acid (PTSA) is solid), is soluble in many organic solvents, forms water-soluble salts with all inorganic cations and with most organic cations, does not form complexes with metal ions in water, its anion, mesylate, is non-toxic and suitable for pharmaceutical preparations. Methanesulfonic acid can be used in the generation of borane (BH3) by reacting methanesulfonic acid with NaBH4 in an aprotic solvent such as THF or DMSO, the complex of BH3 and the solvent is formed.

Applications Solutions of methanesulfonic acid are used for the electroplating of tin and tin-lead solders. It is displacing the use of fluoroboric acid, which releases corrosive and volatile hydrogen fluoride. Methanesulfonic acid is also a primary ingredient in rust and scale removers. It is used to clean off surface rust from ceramic, tiles and porcelain which are usually susceptible to acid attack.

See also Trichloromethanesulfonic acid, a trichloro analogue Trifluoromethanesulfonic acid, the more acidic trifluoro analogue

References

Illustrations

Worked examples

Example 1 — a first encounter with Methanesulfonic acid

Start with the simplest possible case. Write down what Methanesulfonic acid 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 Methanesulfonic acid 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 Methanesulfonic acid 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 Methanesulfonic acid

In research: Methanesulfonic acid 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 Methanesulfonic acid 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: Methanesulfonic acid is common in secondary-school and first-year university syllabi. It links to neighbouring topics Acid catalysts, Methyl compounds, Organic compounds with 1 carbon atom, so understanding it makes those chapters shorter.
In everyday life: Look for Methanesulfonic acid 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 Methanesulfonic acid in 20 minutes

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

Frequently asked questions

What is Methanesulfonic acid in simple terms?

Why does Methanesulfonic acid 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 Methanesulfonic acid?

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 Methanesulfonic acid.