AMINES

• Amines


  Produced when one or more of the hydrogen atoms in ammonia is replaced with an organic group
• Nucleophilic Substitution


  1. Reaction of a halogenoalkane with ammonia in a sealed tube

  2. One mole of halogenoalkane reacts with two moles of ammonia producing a primary amine and an ammonium salt
• Substitution reaction can continue until all the hydrogen atoms have been replaced with organic groups
• Additional substitution can occur, producing a quaternary ammonium salt
• Mixture of products are produced, so the reaction has low efficiency
• Reaction conditions changed


  • To achieve only the primary amine
  • Ammonia added in excess
  • Mixture of products separated using fractional distillation
• Reduction of Nitriles


  1. Reducing nitriles via hydrogenation

  2. Requires LiAlH4, a reducing agent, and acidic conditions or a combination of hydrogen and Nickel (catalytic hydrogenation)
• Aromatic Amines


  Produced from the reduction of nitrobenzene using concentrated hydrochloric acid (HCl) and a Tin catalyst
• Cationic Surfactants


  • Molecules with a positive and negative end
  • Good conditioners as the two ends are attracted to different substances, preventing static from building up on surfaces
• Amines are weak bases


  Lone electron pair on the nitrogen atom can accept protons
• Base strength of amines

  • Depends on how available the electron pair is on the molecule
  • More available the electrons, the more likely it is to accept a proton, meaning it is a stronger base
• Inductive Effect


  • Benzene rings draw electron density away from the nitrogen, making it 'less available'
  • Alkyl groups push electron density towards the nitrogen, making it 'more available'
  • More alkyl groups means more 'pushing'
• Aliphatic amines are stronger bases and aromatic amines are weaker
• Nucleophilic Substitution


  • Amines can act as nucleophiles because the lone electron pair is attracted to δ+ regions on other molecules
  • Amines can substitute halides on halogenoalkanes to form 1°, 2° or 3° amines and quaternary ammonium salts
• Nucleophilic Addition-Elimination


  Amines can undergo nucleophilic addition-elimination reactions with acyl chlorides to produce amides and N-substituted amides
• Mechanism of Nucleophilic Addition-Elimination

  1. Amine acts as a nucleophile, attacking the acyl chloride

  2. Chloride ion is eliminated

  3. Amide is formed
• Same reaction mechanism can also occur with acid anhydrides to produce an amide and a carboxylic acid
• 1. substituted Amides


  Treated in a similar way to esters when naming
• LiAlH4


  A strong reducing agent used for the reduction of nitriles. It is highly reactive and can cause burns and eye damage.