What functional groups are present in acetaminophen?

The functional groups in acetaminophen are hydroxyl, aromatic ring, and amide.

A functional group is a specific group of atoms within a molecule that gives rise to the characteristic chemical reactions of the molecule.

The structure of acetaminophen is

The group at the top of the molecule is a hydroxyl group. It is tempting to call it an alcohol group.

But an ##"–OH"## group attached to a benzene ring has special properties. It is more commonly called a phenol group or a phenolic ##"OH"##.

The six-membered ring is an aromatic ring.

The group at the bottom of the molecule is a monosubstituted or secondary amide.

The general formula for an amide is ##"RCONR"_2##. In this case, one of the ##"R"## groups on the ##"N"## atom is a hydrogen atom.

(from www.masterorganicchemistry.com)