In organic chemistry, the amino group is understood to be the functional group (–NH 2 ) of the primary amines and most amino acids . More specifically, amines are divided into three categories: primary, secondary and tertiary amines. They differ in the number of carbons that are bound to the central nitrogen. Primary amines have a carbon bond. Secondary two and tertiary three.
The amino group is a basic functional group because the lone pair of electrons on the nitrogen atom - analogous to that in the ammonia molecule - can accept a proton from an acid HA. This turns it into an ammonium salt .
Many drugs are ammonium salts ( hydrofluorides , hydrochlorides , hydrobromides , hydroiodides , maleates , acetates, etc.), as these are more stable (longer storable) and often better absorbable than the free amines.
The Kaiser test is proof of amino groups .