Organic nitrogen compounds: Amines, Amides, A.A, proteins

Preparation of Amines
1. Ammonia heated under pressure with halogenoalkane
  1. 1-3 H substituted by an aryl or alkyl group
2. Reduction of aromatic nitro-compounds to form aryl amines *
  1. Reduction of Nitrobenzene using tin and HCl under reflux: -NO2 → NH2
    1. Cool, +NaOH → redissolve tin(IV) hydroxide
      1. Steam distillation
        Separate phenylamine and water
        Salting out
        Solvent extraction
        Drying agent: Potassium hydroxide
        Final distillation
Properties
1. Aryl amines
  1. Less volatile, usually liquid
  2. Dissolve in organic solvents, only slightly in water
2. Alkyl amines
  1. H-bond → higher m.p
  2. Lower members are gases or volatile liquids
3. Strong Bases: lone pair on N
  1. e- shift from alkyl group → primary alkyl amines better that ammonia
  2. aryl amine: e- on N interact with delocalised pi e- → weaker base than NH3
Reactions
1. NS: With Halogenoalkanes → substituted ammine
2. A-E: With AC → N substituted amides
  1. Condensation polymers: polyamides
3. Amines form complex ions in similar way to NH3
4. ES of phenylamine → 4-aminobenzenesulfonamide
  1. Sulfonamides destroy bacteria
Amino Acids
1. Contain NH2 and COOH and R group
2. Acidic and basic properties
  1. In alkaline soln: acid
  2. In acidic son: base
  3. In neutral soln: zwitterion formed
    1. aa can exist as zwitterions in solid state → high mp, dissolve in water. Don't dissolve in organic solvent
3. 20
4. Peptide bond C-N in condensation reaction
5. Proteins made up of particular sequence of aa
  1. Can determine structure of protein, e.g. Insulin by Frederick Sanger
  2. Difficult for chemists to synthesise proteins
    1. Longer chain = more difficult
6. Hydrolysis of proteins
  1. Reflux with d.HCl
    1. aa neutralised
      1. aa separated by paper chromatography
        Invisible, so spray with ninhydrin in fume cupboard and dry → purple spots
        Rf value to identify aa
        Sometimes electrophoresis is used
7. Optical activity
  1. Most aa form optical isomers
  2. aa in living organisms are L enentiomers
  3. Laboratory synthesis of aa tends to produce racemic mixture of L and D enantiomers
Ecstasy (an amine) causes release of serotonin and dopamine in the brain
Paracetamol
1. Phenol is nitrated using H2SO4 and Sodium nitrate
  1. 2-nitrophenol and 4-nitrophenol
  2. Fractional distillation
    1. 4-nitrophenol is reduced → 4-aminophenol
      1. Using Sodium tetrahydridoborate(III) in alkaline soln
      2. + ethanoic anhydride →paracetamol
    2. 4-nitrophenol ↑bp
2. No chiral centres → simpler
Azodyes
1. Phenylamine + nitrous acid (made in situ) +HCl
  1. <5 degrees
  2. benzenediazonium chloride + water
    1. Diazonium compound reactions
      1. NS: N evolved
      2. Is strong electrophile
        Coupling → strong coloured compounds, no N produced
        Diazo-compounds are extremely stable and unreactive
        Extensive delocalised e- system → bright colours
        Dye
Polymers
1. Nylon
  1. Wallace Hume Carothers
  2. Made from 2 monomers
    1. Hexanedioic acid + 1,6-diaminohexane → nylon-6,6
    2. Obtained via phenol or cyclohexane
  3. Uses: tights, carpets, ropes
2. Kevlar
  1. 1st used in 1970s as a replacement for steel in racing car tyres
  2. Resists high temp, low thermal conductivity, high tensile strength, flame, chemical and cut resistant
  3. Uses: cables, tyres, bullet proof vests, ropes, adhesives
3. Addition polymerisation
  1. 2-propanamide → Poly(propanamide)
    1. Crossed linked → gel which absorbs water → soft contact lenses
    2. Non-cross-linked → thickener and filler in facial surgery
  2. Ester exchange: Poly(ethylethanoate) + methanol → poly(ethanol) + methylethanoate
    1. Solubility varies
    2. uses: disposable laundry bags (bags dissolve in wash cycle), viscoelastic gel
  3. Properties of polyamides
    1. Links vulnerable to attack under acidic or alkaline conditions
    2. Addition polymers of just C and H are difficult to break down → pollution

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Organic nitrogen compounds: Amines, Amides, A.A, proteins

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	Created by Cindy Lam over 11 years ago