WM

• Separation using a separating funnel

  1. Add distilled/redistilled substance to separating funnel

  2. Add water to dissolve soluble impurities

  3. Drain off aqueous layer containing soluble impurities

  4. Add anhydrous calcium chloride to organic layer to remove water

  5. Filter to remove solid drying agent
• Vacuum filtration

  1. Use a Buchner funnel and vacuum to separate solid and liquid

  2. Wet filter paper to seal funnel

  3. Pour reaction mixture through

  4. Vacuum draws liquid through leaving solid trapped
• Solvent choice for recrystallisation

  Must fully dissolve impure solid when hot, but be virtually insoluble when cold
• Purifying a solid

  1. Dissolve in hot solvent

  2. Filter to remove insoluble impurities

  3. Dry the purified solid
• Ideal solvent properties


  • Fully dissolves the impure solid when hot
  • Virtually insoluble when cold
• If the solid is still soluble when cold, it cannot be filtered and purified
• Melting point analysis


  1. Add sample to capillary tube

  2. Place in melting point apparatus

  3. Slowly heat and observe melting range

  4. Compare to reference data
• RF value


  Ratio of distance travelled by spot to distance travelled by solvent front
• TLC


  • Number of spots indicates number of components in mixture
  • RF values can be used to identify compounds by comparison to reference data
• Column chromatography

  • Separates components based on differential partitioning between stationary and mobile phases
  • Allows purification of larger quantities compared to TLC
• Infrared spectroscopy


  1. Expose sample to infrared radiation

  2. Observe absorption peaks corresponding to vibrations of functional groups
• Infrared spectroscopy alone is often not sufficient to fully identify an unknown compound
• Infrared spectrum


  Technique used to identify functional groups in a compound
• Ethanoic acid


  Compound being analysed in the infrared spectrum
• Broad peak


  • Indicates presence of O group
• Peak at ~1700 cm-1


  • Indicates presence of carbonyl group
• Oxidation reaction can be used with infrared to confirm presence of alcohol group
• Molecular ion peak


  Peak representing the unfragmented molecular ion
• Mass spectrometry fragmentation patterns

  • Can be used to distinguish between isomeric compounds with the same molecular formula
• Green chemistry


  Approach to using resources sustainably and protecting the environment
• Principles of green chemistry


  • Using renewable feedstocks
  • Reducing energy consumption
  • Using renewable energy
  • Reducing toxicity
  • Improving safety
  • Monitoring technology
  • Improving atom economy
  • Using catalysts
  • Designing for end-of-use
• Alcohols


  Functional group is the OH (hydroxyl) group
• Primary alcohols

  • Alcohol group attached to a carbon which is attached to one other carbon
• Secondary alcohols

  • Alcohol group attached to a carbon which is attached to two other carbons
• Tertiary alcohols

  • Alcohol group attached to a carbon which is attached to three other carbons
• Oxidation of alcohols


  1. Primary alcohols can be oxidised to aldehydes and then to carboxylic acids

  2. Secondary alcohols can be oxidised to ketones

  3. Tertiary alcohols cannot be oxidised by dichromate, can only be oxidised by burning
• Distillation


  1. Used to separate aldehydes from primary alcohols during oxidation

  2. Allows volatile products to be removed as soon as they are formed
• Reflux


  1. Used to further oxidise aldehydes to carboxylic acids

  2. Allows strong heating without losing volatile reactants and products
• Dehydration of alcohols can be illustrated using an elimination mechanism
• Dehydration of alcohols

  1. Alcohol

  2. Acid catalyst

  3. Lone pair of electrons in oxygen moves to H+

  4. Positive charge on oxygen

  5. Electrons from C-H bond move to form double bond

  6. H+ catalyst reformed
• Elimination reaction

  Removing a molecule from a compound to form a double bond
• Ester formation from carboxylic acid and alcohol

  1. Carboxylic acid (blue)

  2. Alcohol (red)

  3. Acid catalyst

  4. OH from acid and H from alcohol form water

  5. Ester formed
• Halogenation of alcohols


  1. Alcohol

  2. HCl

  3. OH group replaced by halogen

  4. Water formed
• Phenols

  Aromatic compounds with OH group attached to benzene ring
• Test for phenols

  Add iron(III) chloride - forms purple colour
• Phenols

  • Weak acids that partially dissociate
  • Form phenoxide ion
• Reaction of phenols with alkalis

  Phenol + NaOH -> Sodium phenoxide + water
• Phenols vs carboxylic acids

  Phenols don't react with carbonates, carboxylic acids do
• Phenols vs alcohols


  Phenols react with acid anhydrides, alcohols react with both acid anhydrides and carboxylic acids