organic chem: amines

• in a amine, the hydrogen in a ammonia is replaced by an alkyl group
• aliphatic amine

  the hydrogen is replaced by a alkyl group (methyl)
• aromatic amine


  the hydrogen is replaced by a aryl group (benzene)
• amides have a C double bond O
• amides can be formed from...

  1. condensation reaction of COOH
  2. acyl chloride with ammonia
• amino acids contain a amino group and a carboxylic acid
• primary aliphatic amines : reactions

  • decrease solubility in water as chain length increases
  • phenylamine is only slightly soluble in water
  • can form hydrogen bonds
• amine basicity

  • react as bronsted-lowry bases
  • accept a proton due to the lone pair of electrons on the nitrogen
• strengths of amines

  • depends on the ability of the lone pair of electrons in the nitrogen to accept a proton
• factors affecting basicity

  1. positive inductive effects

  • alkly group donates electron density to the nitrogen atom causing the lone pair to become more available
• factors affecting basicity

  1. positive inductive effects

  • alkly group donates electron density to the nitrogen atom causing the lone pair to become more available
  • 2. delocalisation
  • with aromatic rings the lone pair becomes delocalised meaning it is less available which decreases basicity
• from strongest to weakest basicity in amines

  1. ethylamine - alkyl group donates electron density to the nitrogen group causing the lone pair to be more available
  2. ammonia - neutral
  3. phenylamine - nitrogen lone pair of electrons become delocalised
• reactions with acids

  • amine forms ammonium salts
  • adding NaOH to ammonium salt will convert it back to amine
  • can be crystals if water is evaporated
  • ammonium salts are soluble in acid
• primary aliphatic amine reactions with ethanoyl chloride

  • addition-elimination reactions
  • forms amide and HCL
• primary aliphatic amine reaction with halogenoalkanes

  • substitution reaction
  • forms a secondary amine and HCl

  secondary amine contains electron rich nitrogen which can react with chloroethane to form tertiary amine

  • no HCl as tertiary amine does not lose a hydrogen
  • forms quaternary ammonium salts
• primary aliphatic amines reaction with copper ions

  • amine act as a lone-pair donor with transition metals
  • obersvations
  • blue precipitate forms
  • excess ammonia makes blue solution
• primary aliphatic amines - preparations

  1. halogenoalkanes with ammonia
  2. reduction of nitriles
• halogenoalkanes with ammonia to form primary aliphatic amines

  • nucleophilic substitution reaction
  • halogenalkane must be reacted with excess, hot ethanolic ammonia under pressure to form a primary amine
  • nitrogen acts as a nucleophile and replaces the hydrogen
• reduction of nitriles

  • nitrile vapour and hydrogen gas are passed over a LiAlH4 in dry ether to form primary amine
• aromatic amines - formation

  • nitrobenzene can be reduced to form phenylamine
• stage 1 of reduction of nitrobenzene

  • react with tin and HCl under reflux in a water bath
  • nitrobenzene gains electrons from tin
  • doesn't form phenylamine directly due to the presence of acid
• stage 2 : formation of phenylamine

  • adding excess NaOH causes the phenylammonium ion to lose its protons
  • mixture of tin hydroxide is also formed
• stage 3: purification of phenylamine

  • undergoes steam distillation to produce cloudy distilate
  • NaCl is added to distilate
  • add separating funnel
  • ester is added resulting in an aqueous layer at the bottom and the organic layer at the top
  • NaCl increases ploraity of the aqueous layer
  • organic layer is distilled: ester boils off easily, phenylamine boils at 180 degrees
• aromatic amines: reactions (azo compounds)

  • azo compounds contain a N triple bond N group
  • formed in coupling reactions between the diazonium ion and alkaline solution of phenol
• formation of azo compounds

  using benzenediazonium chloride salt and alkaline phenol