Methanesulfonic acid
[CAS# 75-75-2]

Identification

• Classification: Chemical reagent >> Organic reagent >> Fatty acid
• Name: Methanesulfonic acid
• Synonyms: Methylsulfonic acid; Alkanesulfonic acid; MSA; Methanesulfonic acid
• Molecular Formula: CH₄O₃S
• Molecular Weight: 96.10
• CAS Registry Number: 75-75-2
• EC Number: 200-898-6
• SMILES: C1=CC(=NC(=C1)C(=O)Cl)C(=O)Cl

Properties

• Density: 1.481
• Melting point: -60 °C
• Boiling point: 167 °C (10 torr)
• Refractive index: 1.413-1.415
• Flash point: 189 °C

Safety Data

• Hazard Symbols: GHS05 Danger
• Risk Statements: H314
• Safety Statements: P260-P264-P280-P301+P330+P331-P302+P361+P354-P304+P340-P305+P354+P338-P316-P321-P363-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin corrosion	Skin Corr.	1B	H314
Acute toxicity	Acute Tox.	4	H312
Acute toxicity	Acute Tox.	4	H302
Serious eye damage	Eye Dam.	1	H318
Substances or mixtures corrosive to metals	Met. Corr.	1	H290
Specific target organ toxicity - single exposure	STOT SE	3	H335
Acute toxicity	Acute Tox.	3	H301
Reproductive toxicity	Repr.	2	H361
Skin corrosion	Skin Corr.	1A	H314
Skin corrosion	Skin Corr.	1C	H314
Acute toxicity	Acute Tox.	4	H332
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412

• Transport Information: UN 2585; UN 2586; UN 3265

Discovery and Applications

Methanesulfonic acid (MSA) is a simple alkanesulfonic acid with the chemical formula CH₄O₃S and a molecular weight of 96.11 g/mol. It is a colorless liquid that is strongly acidic, non-oxidizing, and highly soluble in water and organic solvents. The unique properties of MSA make it a valuable chemical in a variety of industrial and scientific applications.

The discovery of methanesulfonic acid dates back to early studies on sulfonic acids in the 19th century. MSA was originally synthesized by oxidation of methyl mercaptan (methyl mercaptan) or dimethyl sulfide, a process that was optimized over time. Early studies on methanesulfonic acid highlighted its strong acidity and stability compared to other sulfonic acids, leading to its adoption in various chemical processes.

Methanesulfonic acid is typically synthesized by oxidation of methyl mercaptan or dimethyl sulfide using an oxidant such as nitric acid (HNO₃) or hydrogen peroxide (H₂O₂). The industrial process is oxidation of dimethyl sulfide using oxygen in the presence of a catalyst, which allows for efficient production of MSA on a large scale, supporting its widespread use in industry.

Methanesulfonic acid is widely used as a catalyst in organic synthesis. Its strong acidity and non-oxidizing properties make it suitable for esterification, alkylation, and polymerization. Unlike mineral acids, MSA does not introduce water into the reaction, which helps prevent side reactions and improves product yield.

In the electroplating industry, MSA is used as an electrolyte for the deposition of metals such as tin and lead. Its high solubility and conductivity improve the quality of metal coatings, making it a top choice for electronic and surface treatment applications.

In pharmaceuticals, MSA is used to form salts with active pharmaceutical ingredients (APIs). Mesylate salts are generally more soluble and bioavailable than their parent compounds, thereby enhancing the efficacy and stability of the drug. MSA It is also used to synthesize active pharmaceutical intermediates, which aids in the development of new drugs.

MSA can be applied to advanced battery technologies, such as lead-acid batteries. It acts as an electrolyte, which improves battery efficiency and life, helping to improve the performance of energy storage systems.

Due to its strong acidity and ability to dissolve scale and rust, MSA is used in industrial cleaning formulations. It effectively removes deposits from equipment and surfaces without corrosive metals, making it an ideal choice for maintenance in a variety of industries.

References

1964. Methanesulfonate Esters of Cholane Alcohols. Journal of Pharmaceutical Sciences, 53(9).
DOI: 10.1002/jps.2600530904

1964. Carcinostatic Methanesulfonic Acid Esters of Some Aminoglycols. Chemical and Pharmaceutical Bulletin, 12(8).
DOI: 10.1248/cpb.12.954

1990. Efficient solid-phase peptide synthesis using an α-amino deprotecting procedure with methanesulfonic acid. Peptides.
DOI: 10.1007/978-94-010-9060-5_312