6.7/6.8 extending carbon chains and organic synthesis

• Friedel-Crafts reactions


  • Alkylation
  • Acylation
• Recrystallisation


  Purification of impure solids, not soluble in solvent
• Preparation of an organic solid (aspirin)


  1. Recrystallisation

  2. Determination of melting point
• Repeated recrystallisation ensures purity but decreases yield
• Melting point


  • Shows identity and purity of solid
  • Pure substances have a defined melting point, impure have a range
• Solid must be a dry fine powder in melting point tube
• Hot oil rises and circulates, heat at centre, repeats
• Conditions for alkane to haloalkane


  1. Halogen (e.g. Br2) and UV light

  2. Mechanism: free radical substitution
• Conditions for alkene to alkane


  1. H2 and Ni catalyst, 200°C, 100 KPa

  2. Mechanism: hydrogenation or reduction
• Conditions for alkene to haloalkane


  1. Hydrogen halide (e.g. HBr), room temp

  2. Mechanism: halogenation, electrophilic addition
• Products of alkene halogenation

  • Markownikov, halogen ends up bonded to the most substituted carbon atom to form the most stable carbocation (major product)
• Conditions for haloalkane to alcohol


  1. NaOH(aq) on KOH with ethanol, heat

  2. Mechanism: nucleophilic substitution
• Conditions for alcohol to haloalkane


  1. HX (by reacting KX with H2SO4 or H3PO4 or NaX) e.g. NaBr/H2SO4

  2. Mechanism: substitution
• Conditions for alcohol to alkene


  1. Hot catalyst Al2O3 powder or pieces of porous pot, excess hot concentrated H2SO4 or H3PO4 catalyst

  2. Mechanism: elimination, dehydration
• Conditions for alkene to alcohol

  1. H2O(g) at 300°C 60 atm pressure and H2SO4 or H3PO4 catalyst

  2. Mechanism: hydration
• Conditions for haloalkane to nitrile


  1. KCN in ethanol (form -CN), heat under reflux

  2. Mechanism: nucleophilic substitution
• Conditions for haloalkane to amine


  1. Ammonia (NH3) in ethanol, heat

  2. Mechanism: nucleophilic substitution
• Conditions for alcohol to ketone


  1. Secondary alcohol, K2Cr2O7/H2SO4 and heat under reflux

  2. Mechanism: oxidation
• Oxidation of alcohol Colour change: orange to green
• Conditions for alcohol to aldehyde


  1. K2Cr2O7/H2SO4, distill, primary alcohol

  2. Mechanism: oxidation
• Conditions for alcohol to ester


  1. Carboxylic acid, concentrated H2SO4 catalyst, heat under reflux, or acid anhydride at room temp

  2. Mechanism: esterification, condensation
• Aldehyde to alcohol


  • Conditions: NaBH4, 2[H]
  • Mechanism: Nucleophilic addition, reduction
• Ketone to hydroxynitrile 


  • Conditions: HCN or NaOH(aq), H+ (aq)
  • Mechanism: Nucleophilic addition
• Aldehyde to hydroxynitrile


  • Conditions: NaCN(aq), H+ (aq)
  • Mechanism: Nucleophilic addition
• Alcohol to carboxylic acid


  • Conditions: K2Cr2O7 + H2SO4, reflux, primary alcohol 2[O]
  • Mechanism: Oxidation
• Aldehyde to carboxylic acid


  • Conditions: K2Cr2O7 + H2SO4, reflux, [O]
  • Mechanism: Oxidation
• Carboxylic acid to ester


  • Conditions: alcohol, concentrated H2SO4, heat
  • Mechanism: Esterification, condensation
• Carboxylic acid to acyl chloride


  • Conditions: SOCl2 (l), fume cupboard
  • Mechanism: Substitution
  • Waste product: SO2 + HCl(g)
• Acyl chloride to carboxylic acid


  • Conditions: H2O
  • Mechanism: Addition-elimination reaction
  • Waste product: HCl
• Acyl chloride to ester


  • Conditions: alcohol or phenol and heat, and a base
  • Mechanism: Esterification, addition-elimination
• Acyl chloride to primary amide 


  • Conditions: ammonia
  • Mechanism: Condensation, addition-elimination
• Acyl chloride to secondary amide 


  • Conditions: primary amine
  • Mechanism: Condensation, addition-elimination
• Hydroxynitrile to Amine


  • Conditions: H2(g) and Ni catalyst
  • Mechanism: Reduction
• Ketone to alcohol


  Conditions: reducing agent NaBH4, generates nucleophile H-, 2[H]

  mechanism: nucleophile addition, reduction
• Nitrile to primary amine


  Conditions: H2(g) and Ni Catalyst, nitrile vapour or LiAlH4(4[H])

  mechanism: reduction