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p-Toluenesulfonic acid

IUPAC: 4-methylbenzenesulfonic acid

C7H8O3S Laboratory Reagents CAS 104-15-4
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Quick Reference
Formula / NotationC7H8O3S
CAS Number104-15-4
Molecular Weight172.20
Melting Point221 °F (USCG, 1999)
Boiling Point140 °C @ 20 MM HG
Density1.45 at 77 °F (USCG, 1999) - Denser than water; will sink
SolubilityABOUT 67 G/100 ML WATER; SOL IN ALCOHOL, ETHER
AppearanceToluene sulfonic acid, liquid, with more than 5% free sulfuric acid appears as colorless to black solid. Odorless or nearly odorless. (USCG, 1999)
Also Known As4-methylbenzenesulfonic acid; 4-Methylbenzenesulfonic acid; 104-15-4; 4-Toluenesulfonic acid; p-Toluenesulphonic acid; Tosic acid; Toluene-4-sulfonic acid; p-Tolylsulfonic acid; Tosylic acid; Toluenesulfonic acid
CategoryLaboratory Reagents

What is p-Toluenesulfonic acid?

Toluene-4-sulfonic acid is an arenesulfonic acid that is benzenesulfonic acid in which the hydrogen at position 4 is replaced by a methyl group. It is a member of toluenes and an arenesulfonic acid. It is a conjugate acid of a toluene-4-sulfonate.

Formula & Notation

C7H8O3S

IUPAC Name: 4-methylbenzenesulfonic acid

Other Names / Synonyms: 4-methylbenzenesulfonic acid; 4-Methylbenzenesulfonic acid; 104-15-4; 4-Toluenesulfonic acid; p-Toluenesulphonic acid; Tosic acid; Toluene-4-sulfonic acid; p-Tolylsulfonic acid; Tosylic acid; Toluenesulfonic acid

Properties & Characteristics

Appearance: Toluene sulfonic acid, liquid, with more than 5% free sulfuric acid appears as colorless to black solid. Odorless or nearly odorless. (USCG, 1999). Molecular formula: C7H8O3S. Molecular weight: 172.20 g/mol. Boiling point: 140 °C @ 20 MM HG. Melting point: 221 °F (USCG, 1999). Density: 1.45 at 77 °F (USCG, 1999) - Denser than water; will sink. Solubility: ABOUT 67 G/100 ML WATER; SOL IN ALCOHOL, ETHER. Vapor pressure: 0.0000027 [mmHg]. LogP: 1.7.

Physical Data

PropertyValue
Melting Point221 °F (USCG, 1999)
Boiling Point140 °C @ 20 MM HG
Density1.45 at 77 °F (USCG, 1999) - Denser than water; will sink
Molecular Weight172.20
SolubilityABOUT 67 G/100 ML WATER; SOL IN ALCOHOL, ETHER
AppearanceToluene sulfonic acid, liquid, with more than 5% free sulfuric acid appears as colorless to black solid. Odorless or nearly odorless. (USCG, 1999)

Uses & Applications

Used as a synthetic reagent for transformations including oxidation, reduction, coupling, or functional group manipulation.

Safety Information

Hazardous reagent. May be toxic, corrosive, flammable, or reactive. Use in fume hood with full PPE. Consult SDS before use.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term p-Toluenesulfonic acid
Formula C7H8O3S
CAS Number 104-15-4
Molecular Weight 172.20
Synonyms 4-methylbenzenesulfonic acid; 4-Methylbenzenesulfonic acid; 104-15-4; 4-Toluenesulfonic acid; p-Toluenesulphonic acid; Tosic acid; Toluene-4-sulfonic acid; p-Tolylsulfonic acid; Tosylic acid; Toluenesulfonic acid

Frequently Asked Questions

Toluene-4-sulfonic acid is an arenesulfonic acid that is benzenesulfonic acid in which the hydrogen at position 4 is replaced by a methyl group. It is a member of toluenes and an arenesulfonic acid. It is a conjugate acid of a toluene-4-sulfonate.

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Editorial standards: Chemical data is sourced from peer-reviewed literature, CAS Registry, NIST WebBook, and PubChem. Safety information reflects guidance from OSHA, ECHA, and IAEA. For educational purposes only — always consult official SDS documentation and qualified professionals before handling chemicals.