Untitled Quiz

Introduction to Amines

• Amines are organic compounds containing nitrogen, known for their basic properties.
• They are derived from ammonia, where one, two, or all three hydrogen atoms are replaced by alkyl or aryl groups.

Classification of Amines

• Primary (1°): One alkyl or aryl group attached to nitrogen (R-NH2).
• Secondary (2°): Two alkyl or aryl groups attached to nitrogen (R2NH).
• Tertiary (3°): Three alkyl or aryl groups attached to nitrogen (R3N).

Naming of Amines

• Common Names: Use prefix "alkyl" followed by "amine" (e.g., methylamine, dimethylamine).
• IUPAC Names: Use prefix "amino" followed by the parent alkane name (e.g., aminomethane, aminoethane).

Physical Properties of Amines

• Physical State: Lower aliphatic amines are gases with a fishy odour. Middle members are liquids, and higher members are solids.
• Intermolecular Forces: N-H bonds are polar due to the electronegativity difference between nitrogen and hydrogen.
  • Primary amines exhibit stronger hydrogen bonding compared to secondary amines.
  • Tertiary amines lack intermolecular hydrogen bonding.

Solubility of Amines

• Lower aliphatic amines are highly soluble in water due to hydrogen bonding.
• Solubility decreases with increasing molecular weight and the number of carbon atoms.

Basicity of Amines

• Amines are basic due to the lone pair of electrons on the nitrogen atom.
• Factors Affecting Basicity:
  • Electron-donating groups: Increase basicity by increasing electron density on nitrogen.
  • Electron-withdrawing groups: Decrease basicity by decreasing electron density on nitrogen.
  • Hybridization: sp3 hybridized nitrogen is more basic than sp2 hybridized nitrogen.

Basicity of Aromatic Amines

• Aromatic amines are less basic than aliphatic amines due to electron delocalization in the ring, which reduces the electron density on nitrogen.

Reactions of Amines

• Reaction with HNO2 (Nitrous Acid):

  • Primary amines react with nitrous acid (HNO2) to form diazonium salts.
  • Secondary amines react with HNO2 to form nitrosamines.
  • Tertiary amines don't react with nitrous acid.

• Reaction with Arene sulphonyl chloride:

  • Used to distinguish between primary, secondary, and tertiary amines based on their reactivity and solubility in NaOH solution.

Electrophilic Aromatic Substitution in Aromatic Amines

• Bromination: Aromatic amines undergo electrophilic substitution reactions, readily brominating at the ortho and para positions due to the electron-donating effect of the amino group.
• Nitration: Aromatic amines can be nitrated using a mixture of concentrated nitric acid and sulfuric acid.
• Sulfonation: Aromatic amines undergo sulfonation with concentrated sulfuric acid to form sulfonic acids.