(i) Amines undergo protonation to give amide ion.
Similarly, alcohol loses a proton to give alkoxide ion.
In an amide ion, the negative charge is on the N-atom whereas in alkoxide ion, the
negative charge is on the O-atom. Since O is more electronegative than N, O can accommodate the negative charge more easily than N. As a result, the amide ion is less stable than the alkoxide ion. Hence, amines are less acidic than alcohols of comparable molecular masses.
(ii)In a molecule of tertiary amine, there are no H−atoms whereas in primary amines, two
hydrogen atoms are present. Due to the presence of H−atoms, primary amines
undergo extensive intermolecular H−bonding.
As a result, extra energy is required to separate the molecules of primary amines. Hence, primary amines have higher boiling points than tertiary amines
(iii) Due to the −R effect of the benzene ring, the electrons on the N- atom are less available in case of aromatic amines. Therefore, the electrons on the N-atom in
aromatic amines cannot be donated easily. This explains why aliphatic amines are
stronger bases than aromatic amines.
