4.2.3 - organic synthesis

• In distillation, a continuous water flow is needed so the water remains cool in order for the mixture to be distilled.
• To separate immiscible liquids:

  • Pour mixture into separating funnel, and distilled water
  • add stopper and invert the flask
  • equalise the pressure by opening the stopper
  • continue shaking until there is no ‘whistle’ sound
  • open the stopper and place a beaker under the spout
  • use another beaker to collect desired organic layer
  • shake liquid with drying agent
• Two drying agents are:

  magnesium sulfate

  calcium chloride
• To use drying agents you add it to the organic product. Add some more until the clumps are moving freely. Use filtration to collect the dry product.
• Re-distillation is when a liquid is purified by using multiple distillations.
• Unsaturated hydrocarbons can be tested using bromine water.

  Add a few drops to the sample, positive result shows colour change from brown to colourless.
• to test for haloalkanes add silver nitrate, ethanol and water. observe:

  Chloro - white precipitate

  bromo - cream precipitate

  iodo - yellow precipitate
• 3 reagents used to test for carbonyls are

  acidified potassium dichromate

  fehlings solution

  tollens reagent
• When acidified potassium dichromate is added to ketones there is no change. But when it is added to aldehydes it turns from orange to green colour.
• When feelings solution is reacted with ketones there is no change. But when it is reacted with aldehydes it forms a dark red precipitate.
• When tollens reagent is reacted with ketones no silver mirror is formed. When it is reacted with aldehydes it forms a silver mirror.
• To test for a carboxylic acid.

  Universal indicator gives the ph of a weak acid

  reactive metal gives hydrogen effervescence

  metal carbonate gives carbon dioxide effervescence