Basicity

• Basicity is the ability of a base to donate a lone pair of electrons to a hydrogen atom in a water molecule. It is quantified using Ka or pKa.
• The pKa of water is 7.00.
• Primary aromatic amines, such as phenylamine, don't form basic solutions because the lone pair of electrons on the nitrogen atom delocalise with the ring of electrons in the benzene ring, so N is less able to accept protons.
• Increasing hydrocarbon length of amines causes an increase in basicity.
• Secondary amines are stronger bases than primary amines because they have more alkyl groups on the N atom in place of hydrogen atoms. Therefore, electron density is pushed onto the N atom.
• The first few primary aliphatic amines are completely miscible in water (since they can form hydrogen bonds), but as the hydrocarbon chain increases in length, solubility decreases.