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
• Nucleophilic Substitution reaction

  • Mixture of products produced
  • Low efficiency
  • Reaction conditions have to be changed to achieve only the primary amine
  • Ammonia can be added in excess
  • Mixture of products can be separated using fractional distillation

  
• Reduction of Nitriles

  1. Reducing nitriles via hydrogenation can produce amines

  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

  
• Amine Base Properties

  • Amines are weak bases because the 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

  
• 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 1o, 2o or 3o 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. Nucleophilic attack by amine on acyl chloride

  2. Tetrahedral intermediate formed

  3. Elimination of HCl to form amide

  
• 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