According to the number of hydrogen atoms that are substituted, amines are classified in the following order: primary amines (RNH2), secondary amines (R2NH), tertiary amines (R3N), and quaternary ammonium salts (R4N+X-). Examples include methylamine (CH3NH2), aniline (C6H5NH2), ethylenediamine (H2NCH2CH2NH2), diisopropylamine ([(CH3)2CH]2NH), triethanolamine (HOCH2CH2)3N, and tetrabutylammonium bromide (CH3CH2CH2CH2)4N+Br-. Tetrahydroxy-substituted ammonium hydroxides or ammonium salts are called quaternary ammonium hydroxides or quaternary ammonium salts. [1] NH4+ammonium R4NOH quaternary ammonium hydroxide R4NX quaternary ammonium salt
According to the different types of hydrocarbon groups attached to nitrogen atoms in the amine molecule, amines can be divided into aliphatic amines and aromatic amines. If an amine molecule contains two or more amino groups (-NH2), it can be classified into diamines and triamines based on the number of amino groups.
