4Methylbenzenesulfonic

4-Methylbenzenesulfonic acid, also known as p-toluenesulfonic acid or TsOH, is an organic sulfonic acid with the formula CH3C6H4SO3H. It is a white solid that is soluble in water, ethanol, and other polar solvents. TsOH is a strong acid, comparable in strength to sulfuric acid, and is often used as a catalyst in organic synthesis.

The acid is commonly encountered in its monohydrate form, TsOH·H2O. It is a widely used reagent in academic and industrial laboratories for a variety of reactions, including esterifications, acetal formations, and rearrangements. Its solid form makes it easier to handle than many other strong acids, and it can often be removed from reaction mixtures by simple filtration or extraction.

4-Methylbenzenesulfonic acid is produced industrially by the sulfonation of toluene. This process typically involves reacting toluene with concentrated sulfuric acid or sulfur trioxide. The product is then purified, often by crystallization. Due to its acidic nature, it is corrosive and should be handled with appropriate safety precautions, including eye protection and gloves.