Amines

• Amines can be classified as primary, secondary or tertiary
• There is some hydrogen bonding between amines except for quaternary structure because the N is attached to no hydrogens.
• Amines are Bronsted Lowry bases due to the lone pair on the nitrogen being ready to accept a proton
• The ability of ammonia or an amino acid to act as a base depends on how well the lone pair on the N atom can accept protons.

  • The higher the electron density of the lone pair on the nitrogen, the better it will be able accept H+ so stronger the base
• Rank of base strength of amines from strongest to weakest is

  1. Tertiary amines
  2. Secondary amines
  3. Primary amines
  4. Ammonia
  5. Aromatic amines (Benzene etc)
• The more alkyl groups that are substituted onto the nitrogen atom in place of hydrogen atom, the more electron density is pushed onto the nitrogen atom which would cause an inductive effect making the base stronger
• For aromatic amines, the lone pair on nitrogen is partially delocalised into the benzene ring leading to a reduction in the electron density of the nitrogen atom so weaker base strength