Organic synthesis practical skills

• Why is it necessary to have a continuous water flow around the condenser in a distillation setup?

  To keep the water cool for effective distillation
• What is the purpose of greasing the joints in a Quickfit apparatus?

  To ensure a tight seal and prevent leaks
• What is the method to separate immiscible liquids using a separating funnel?

  • Pour the mixture into a separating funnel with distilled water
  • Invert the funnel to mix and equalize pressure
  • Shake until no 'whistle' sound is heard
  • Open the stopper to collect the lower layer in a beaker
  • Use another beaker for the desired organic layer
  • Shake with a drying agent
• Name two drying agents used in organic chemistry.

  Magnesium sulphate and calcium chloride
• How do you use drying agents in organic chemistry?

  • Add the drying agent to the organic product
  • If clumps form, add more until they move freely
  • Use gravity filtration to collect the dry product
  • The filtrate is the final product
• What does re-distillation mean?

  Purifying a liquid using multiple distillations
• How can unsaturated hydrocarbons be tested and what are the observations?

  • Use bromine water
  • Add a few drops and mix well
  • Positive test: bromine water turns colourless
• What reagents are used to test haloalkanes and what are the observations?

  • Reagents: silver nitrate, ethanol, and water
  • Observations:
  • Chloro-: white precipitate
  • Bromo-: cream precipitate
  • Iodo-: yellow precipitate
• What are the three reagents that can be used to test carbonyl compounds?

  • Acidified potassium dichromate
  • Fehling’s solution
  • Tollens’ reagent
• What are the observations when acidified potassium dichromate reacts with ketones and aldehydes?

  Keto: no change; Aldehyde: turns from orange to green
• What are the observations when Fehling’s solution is reacted with ketones and aldehydes?

  Keto: no change; Aldehyde: dark red precipitate
• What are the observations when Tollens’ reagent is reacted with ketones and aldehydes?

  Keto: no silver mirror; Aldehyde: silver mirror
• What reagents can be used to test carboxylic acids and what are the corresponding observations?

  • Universal indicator: pH of weak acid
  • Reactive metal: hydrogen effervescence
  • Metal carbonate: carbon dioxide effervescence