The "-OH" group, known as a hydroxyl group, consists of one oxygen atom bonded to one hydrogen atom. It is a key functional group in organic chemistry, commonly found in alcohols and phenols. The presence of the hydroxyl group can significantly influence the properties of a molecule, such as its solubility and reactivity. Hydroxyl groups are polar, which means they can form hydrogen bonds with water and other polar substances. This property makes compounds containing -OH groups, like ethanol and glycerol, more soluble in water compared to non-polar compounds. The ability to form hydrogen bonds also affects boiling points and melting points.