Amines and Amides
Chemistry (Year 12) - Organic Chemistry
The amine functional group occurs when a - NH2 group is single-bonded to a C atom. Amines have the suffix 'amine' and the general formula of R - NH2.
The amide functional group is also the result of a - NH2 group being single-bonded to a C atom, and an additional O atom double bonded to the C atom.
Amides have the general formula of R - CONH2 and the suffix 'amide'. The amide functional group does not need to be numbered as they are always located on a terminal carbon.
Boiling Points of Amines and Amides
Amines typically have high boiling points due to the presence of dispersion forces, dipole-dipole forces and hydrogen bonding.
It is also important to acknowledge that the N atom is a less electronegative element than oxygen. This means that nitrogen is less effective at pulling electrons away from carbons, forming weaker dipoles. This reduced strength of the amine dipole-dipole forces and hydrogen bonds in the N - H bond results in amines having a lower boiling point than alcohols.
Amides in comparison have very high boiling points as they can form a greater number of hydrogen bonds per molecule than amines as well as carboxylic acids.
Additionally, the presence of a highly electronegative O atom bonded to the C atom causes the H atoms to have larger stronger dipoles, and form stronger hydrogen bonds. This results in amides having a higher boiling point than alcohols and carboxylic acids.
Solubility of Amines and Amides
Amines and amides have high solubilities, with amides having a higher solubility than amines.
Amines are less soluble than alcohols as the nitrogen atom is less electronegative than the oxygen atom. Amides are more soluble than carboxylic acids as they can form more hydrogen bonds per molecule with water.