Methyl p-toluenesulfonate

Chemical Properties

white to slightly yellow low melting solid. Soluble in alcohol, ether, benzene, insoluble in water. Hygroscopic.

Uses

Methyl p-Toluenesulfonate can be used in the manufacture of dyes and organic synthesis, and also is the raw materials of methylation.

Uses

Methyl p-toluenesulfonate is used as a methylating agent in organic synthesis. It acts as a catalyst for alkyd resins. It is also employed in selective 1-substitution reaction of tetrazole. Further, it is used in the preparation of dyes.

Preparation

Methyl p-toluenesulfonate was synthesized by the reaction of p-toluenesulfonyl chloride with methanol. Mix p-toluenesulfonyl chloride and methanol, slowly add 25% sodium hydroxide solution, control the temperature below 25 °C, stop adding alkali when the pH is 9, continue stirring for 2 hours, and leave overnight. The lower layer of reactant was taken, the upper layer was extracted with benzene, the extract was recovered with benzene and then combined with the lower layer, washed with water and 5% potassium carbonate solution in turn, dried and distilled under reduced pressure to obtain the finished product of methyl p-toluenesulfonate.

Application

Methyl p-toluenesulfonate is a mild, controllable methylation reagent. Compared to other methylation reagents (such as dimethyl sulfate and methyl iodide), it is characterized by low volatility, lower toxicity, and reduced risk of leakage, making it the reagent of choice for industrial SN2 nucleophilic substitution reactions. In addition, it serves as a sulfonation precursor, undergoing the Friedel–Crafts sulfonation reaction with aromatic hydrocarbons to efficiently synthesize diarylsulfone compounds. It is also prepared as an isotope-labeled methyl donor to synthesize various isotope-labeled bioactive molecules via methylation reactions, which are used in fields such as metabolic tracing and pharmacological research.

Synthesis Reference(s)

Chemical and Pharmaceutical Bulletin, 29, p. 623, 1981 DOI: 10.1248/cpb.29.623
Synthetic Communications, 15, p. 1057, 1985 DOI: 10.1080/00397918508076842

General Description

Methyl p-toluenesulfonate is a solid or liquid with a low melting point. Its melting point is 25–28°C, and it undergoes a phase transition between liquid and solid at room temperature depending on the season. Caking occurs when temperatures are low, which is a normal physical phenomenon. It is hygroscopic, so care must be taken to protect it from moisture during storage.

General Description

Methyl p-toluenesulfonate is sulfonate ester present as potentially genotoxic impurity in drug substances. Kinetics of reactions of methyl p-toluenesulfonate with N,N-dimethylaniline has been investigated. It participates in selective 1-substitution reaction of tetrazole.

Hazard

Toxic by ingestion and inhalation, strongirritant to skin and eyes.

Safety Profile

Poison by ingestion and subcutaneous routes. An eye and severe skin irritant. A vesicant and skin sensitizer. Questionable carcinogen with experimental tumorigenic data. When heated to decomposition it emits toxic fumes of SOx.

Purification Methods

The ester is purified by distillation in vacuo and could be crystallised from pet ether or Et2O/pet ether at low temperature. It is a powerful methylating agent, is TOXIC andis a skin irritant, so it is better to purify it by repeated distillation. [IR: Schreiber Anal Chem 21 1168 1949, Buehler et al. J Org Chem 2 167 1937, Roos et al. Org Synth Coll Vol I 145 1948, Beilstein 11 IV 247.]