28 Organic Synthesis

Question 1

Filtration under reduced pressure

Answer 1

Buchner flask and ring used.
Vacuum pump created by connecting tubing to tap.
Wet filter paper with solvent to prevent it from sliding around.
Rinse out crystals with solvent.

Question 2

Recrystallisation

Answer 2

Warm some of the mixture using a water bath or Bunsen burner.
Add minimum amount of solvent required to dissolve impure sample.
Solution cools and crystals form, filter under reduced pressure.

Question 3

Determining melting point

Answer 3

Used to identify if solid compound is pure (should have sharp melting range).

• Seal end of capillary tube using Bunsen burner then place sample inside.
• Place tube into sample hole and heat up while observing through magnifying window.
• When it starts to melt, record rough temperature. Repeat more carefully to find exact value.

Question 4

Thiele tube/oil bath

Answer 4

Attach capillary tube to thermometer and dip ends into oil.
Heat side arm of Thiele tube/the oil bath with micro burner for a rough value.
Repeat more carefully to obtain accurate value.