PEP Review 83-1-2
p-Cresol from p-Toluenesulfonic Acid
Published: August 1983
Cresol can be made from toluenesulfonic acid by alkali fusion. However, toluenesulfonic acid, made by sulfonation of toluene, is a mixture of p, m, and o isomers, which convert to the corresponding isomers of cresol. o-Cresol can be recovered by fractionation, but the m and p isomers, having very similar boiling points, can be separated from each other only by complex procedures.
This article evaluates a process in which p-toluenesulfonic acid is separated from the sulfuric acid as a hydrate. The bulk of the m- and o- toluenesulfonic acids remaining in the sulfuric acid is isomerized to p-toluenesulfonic acid; the residue is hydrolyzed to toluene and sulfuric acid. In this way, p-toluenesulfonic acid is obtained at high yield and high purity. This is then converted to p-cresol.