Tetramethylammonium toluene-p-sulphonate
[CAS# 3983-91-3]

Identification

• Classification: Chemical reagent >> Organic reagent >> Sulfonate / sulfinate
• Name: Tetramethylammonium toluene-p-sulphonate
• Synonyms: 4-methylbenzenesulfonate;tetramethylazanium
• Molecular Formula: C₁₁H₁₉NO₃S
• Molecular Weight: 245.34
• CAS Registry Number: 3983-91-3
• EC Number: 223-625-2
• SMILES: CC1=CC=C(C=C1)S(=O)(=O)[O-].C[N+](C)(C)C

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H315-H319
• Safety Statements: P264-P264+P265-P280-P302+P352-P305+P351+P338-P321-P332+P317-P337+P317-P362+P364

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319

Discovery and Applications

Tetramethylammonium toluene-*p*-sulphonate is an organic salt composed of the tetramethylammonium cation [(CH₃)₄N]⁺ and the *p*-toluenesulfonate (tosylate) anion [CH₃C₆H₄SO₃]^–. The compound appears as a crystalline solid, combining the high solubility and ionic conductivity of quaternary ammonium salts with the stability of the tosylate counterion.

The compound originates from mid-20th century developments in quaternary ammonium chemistry, when chemists began preparing a variety of tetramethylammonium salts for use as phase-transfer catalysts, ionic liquids, and reagents in organic synthesis. The tosylate anion, derived from *p*-toluenesulfonic acid, was selected for its stability, non-volatility, and ability to form easily handled crystalline salts.

One of the principal applications of tetramethylammonium toluene-*p*-sulphonate is as a phase-transfer catalyst. The tetramethylammonium cation facilitates the transfer of reactive anions (such as halides, cyanide, or hydroxide) between immiscible phases, typically from an aqueous solution into an organic solvent, enabling reactions that would otherwise be inefficient or impossible. This property has been particularly useful in nucleophilic substitution, elimination, and alkylation reactions.

The compound is also used as an electrolyte or supporting salt in electrochemical studies. Quaternary ammonium salts provide high ionic conductivity and electrochemical stability, while the tosylate anion contributes to solubility in polar organic solvents. This makes the compound suitable for voltammetry, electrodeposition, and other electrochemical applications.

In synthetic chemistry, tetramethylammonium tosylate can act as a mild base and as a source of tosylate anions for displacement reactions. It is often employed in substitution reactions where the tosylate group serves as a good leaving group. Additionally, the salt has been investigated for use in ionic liquid formulations, where its relatively low volatility and tunable solubility are desirable.

The preparation of tetramethylammonium toluene-*p*-sulphonate typically involves neutralization of *p*-toluenesulfonic acid with tetramethylammonium hydroxide, followed by crystallization of the salt. The process is straightforward, yielding a stable solid that can be stored and handled without special precautions beyond those typical for organic salts.

Overall, tetramethylammonium toluene-*p*-sulphonate represents a useful quaternary ammonium salt, notable for its roles in catalysis, electrochemistry, and synthetic organic chemistry. Its combination of stability, solubility, and ionic conductivity has made it a versatile compound in both laboratory and industrial settings.

References

2004. Molecular Ionics of Anion Receptor Molecules: A Microcalorimetric Study. Journal of Thermal Analysis and Calorimetry, 77(3).
DOI: 10.1023/b:jtan.0000038988.19849.bb