Question

what is a hydroxyl group

Answer 1

A hydroxy or hydroxyl group is the entity with the formula OH. It contains oxygen bonded to hydrogen. In organic chemistry, alcohol and carboxylic acids contain hydroxy groups. The anion [OH−], called hydroxide, consists of a hydroxy group.

Answer 2

A hydroxyl group (OH group) consists of an oxygen atom covalently bonded to a hydrogen atom. Due to the high electronegativity of the oxygen atom, the bond between the oxygen and the hydrogen is highly polar. Consequently, the hydroxyl group strongly attracts water molecules, forming hydrogen bonds. Hydroxyl groups are responsible for the solubility of some molecules such as sugars  The term alcohol is used to describe molecules which have a hydroxyl group as their only functional group. Dissociation of hydroxyl groups does not usually occur under normal biological conditions.