Phenol

Phenol is a benzene ring with one -OH group attached, C₆H₅OH. Pure, it's a white crystalline solid with a sweet, tarry smell that melts at about 41 °C. It burns skin badly. In the 1860s Joseph Lister used it, as carbolic acid, as one of the first antiseptics in surgery.

Almost all phenol is now made by the cumene process, which makes phenol and acetone together. First, benzene and propylene are joined over an acid catalyst into cumene, a benzene ring carrying a three-carbon branch. Next, air is bubbled through, and oxygen attaches to the branch, forming cumene hydroperoxide. Finally, a little acid splits that into two pieces: the ring with an -OH on it, which is phenol, and the three-carbon branch, which leaves as acetone. Each tonne of phenol comes with about 0.6 tonnes of acetone.

The -OH group makes certain spots on the ring very reactive. That's why two phenol molecules can be clipped onto one acetone to make bisphenol A, the core of epoxy resin. Phenol also goes into nylon and into phenolic resins like Bakelite, one of the first fully synthetic plastics.