Amines

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Amines

  • Derivatives of ammonia where the H's are replaced by C chains.
  • The number of H's replaced corresponds to the structure, primary = 1 H replaced.
  • Often described as having unpleasant odours.
  • -amine is the suffix used.
  • Amines are weak bases, a proton acceptor, this is due to the lone pair of e- on the N atom, which can accept a proton and form a dative covalent bond.~
  • Thus they will react with acids to form salts, an alkylammonium salt:
    -CH3CH2NH2 + HCl -> CH3CH2NH3+Cl-  
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Amines Reactions

  • Preparing aliphatic primary amines:
    -By warming halogenoalkanes with excess ammonia, with an ethanol solvent.
    -CH3CH2CH2Cl + NH3 -> CH3CH2CH2NH2 + HCl
    -Further ammonia forms: NH3 + HCl -> NH4+Cl-
    -To prepare a primary amine, excess ammonia is used to stop further substitution from occuring.
  • Preparing aromatic amines:
    -Nitrobenzene can be reacted with conc. HCl and tin under reflux; and then neutralisation of the excess HCl.
  • Synthesis of dyes:
    -Diazotisation: where phenylamine and nitrous acid is kept below 10 degrees C, a diazonium salt is formed.
    (Nitrous acid, HNO2, is formed with NaNO2 and HCl)
    -This salt then mixes with phenol (etc.) under alkaline conditions (NaOH) and then the coupling of these rings occurs; linked by an azo group -N=N-.
    -This brightly coloured mixture formed is a dye. 
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