Lecture Notes: Organic Synthesis AQA Revision Guide

Overview of Organic Reactions

• Nucleophilic Substitution (Nu Sub):

  • Alcoholic NH3, heat under pressure
  • KOH aqueous, heat under reflux
  • KCN in ethanol/water mixture
  • Halogenoalkane

• Electrophilic Addition (EAdd):

  • Br2, Cl2 UV light
  • HBr, HCl
  • H2SO4, H2O (hydrolysis)

• Elimination:

  • KOH alcoholic
  • Dehydration using conc. H2SO4 or conc. H3PO4

• Oxidation:

  • Primary alcohols using Na2Cr2O7/H+, heat and distil (partial oxidation)
  • Secondary alcohols using Na2Cr2O7/H+, heat
  • Full oxidation of primary alcohols with Na2Cr2O7/H+ under reflux

• Reduction and Other Reactions:

  • NaBH4 and LiAlH4 for Reduction
  • Esterification with Alcohol + H2SO4 or Carboxylic acid + H2SO4
  • Hydrolysis of esters and amides by NaOH and acids

Synthetic Routes and Techniques

Synthetic Routes Design

• Aim to minimize use of solvents and hazardous materials
• Focus on fewer steps for high yield and atom economy
• Minimize side products to reduce separation processes

Organic Techniques

• Distillation:

  • Separate organic products by boiling point
  • Use potassium dichromate and dilute sulfuric acid for oxidizing primary alcohols to aldehydes or carboxylic acids
  • Reflux for long heating without loss of volatile substances

• Fractional Distillation:

  • Separate liquids with different boiling points
  • Thermometer placement is crucial for accuracy

Purification Methods

• Recrystallisation:
  • Dissolve impure compound in hot solvent
  • Cool for crystal formation
  • Suction filtration and washing for impurity removal
• Drying Agents:
  • Use drying agents like anhydrous sodium sulfate to remove water from organic liquids

Functional Group Testing

• Alkenes: Bromine water turns from orange to decolorized.
• Aldehydes:
  • Fehlings Solution turns blue to red precipitate
  • Tollens Reagent forms a silver mirror
• Carboxylic Acid: Sodium carbonate causes effervescence of CO2
• Alcohols and Aldehydes: Sodium dichromate causes an orange to green color change
• Chloroalkane: Silver nitrate forms a white precipitate
• Acyl Chloride: Reacts vigorously with silver nitrate, forming steamy HCl fumes and white precipitate

Testing Reagents

• Tollens Reagent: Oxidizes aldehydes forming a silver mirror
• Fehlings Solution: Oxidizes aldehydes resulting in a red precipitate

Summary

• Sustainable and efficient synthesis routes are key for industrial applications.
• Understanding purification and testing methods is crucial for determining product purity and identity.
• Proper laboratory techniques and safety must be followed during synthetic and testing procedures.