80-48-8

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

white to slightly yellow low melting solid

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

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.

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.

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

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.]