Explain the properties within and between the homologous series of carboxylic acids amines and amides with reference to the intermolecular and intramolecular bonding present

Properties of amines

  • The lower aliphatic amines are gaseous in nature with a fishy smell and can form hydrogen bonds with water molecules and thus are soluble in water.
  • Amines with three or four carbon atoms are liquids at room temperature and those having more carbon atoms hiare solids.
  • Higher the carbon number in amines, lower the capability of being soluble in water.
  • Organic solvents like alcohol, benzene, and ether readily dissolve amines.
  • Primary and secondary amines are often engaged in the intermolecular association as a result of hydrogen bonding between nitrogen of one and hydrogen of the other molecule. The order of intermolecular association is Primary > Secondary > Tertiary.

Properties of carboxylic acids

  • Carboxylic acids exhibit strong hydrogen bonding between molecules and thus have high melting and boiling points.
  • Carboxylic acids having one to four carbons are highly soluble in water due to the presence of dominant hydrogen bonds.
  • However, with the increase in carbon number, the hydrogen bonds become recessive and dispersion forces becoming dominant thus, their solubility decreases.

Properties of amides

  • Generally, have high melting and boiling points.
  • Have polarity as a result of which they are soluble in water except for tertiary amides which show feeble solubility.
  • Because of the greater electronegativity of oxygen, the carbonyl (C=O) is a stronger dipole than the N–C dipole.