C7H7O3S

C7H7O3S is the molecular formula for several chemical compounds, most notably 4-toluenesulfonic acid and its isomers. 4-Toluenesulfonic acid, also known as p-toluenesulfonic acid or TsOH, is an organic sulfonic acid. It is a strong organic acid and a widely used catalyst in organic synthesis. Its chemical structure consists of a benzene ring substituted with a methyl group (CH3) and a sulfonic acid group (SO3H) at opposite positions (para).

The sulfonic acid group is highly polar and readily dissociates in water, making it a strong acid comparable to mineral acids like sulfuric acid, though it is often preferred for its solubility in organic solvents and its milder nature in certain reactions. 4-Toluenesulfonic acid exists as a white solid and is deliquescent, meaning it absorbs moisture from the air.

Isomers of 4-toluenesulfonic acid also share the C7H7O3S formula but differ in the positions of the methyl and sulfonic acid groups on the benzene ring. These include 2-toluenesulfonic acid (ortho) and 3-toluenesulfonic acid (meta). While all are sulfonic acids derived from toluene, their specific properties and reactivity can vary slightly due to the positional differences of the substituents. Applications for these compounds are primarily in catalysis, esterification, dehydration, and polymerization reactions.