4.2.6 : Practical skills for organic synthesis

Question 1

What is distillation?

Answer 1

A technique used to separate miscible liquids (organic and aqueous layers)

Question 2

What apparatus is needed for distillation?

Answer 2

• round bottom flask
• thermometer
• rubber neck (to prevent loss of gas)
• condenser
• collecting flask
• heating mantle
• stand, bosses, clamps

Question 3

Draw distillation diagram

Answer 3

Look at notes!!

Question 4

Describe process of distillation

Answer 4

1. connect condenser to water supply
2. pour organic mixture into a round-bottomed flask with a few anti-bumping granules to ensure smooth boiling
3. heat mixture using heating mantle
4. collect distillate in collecting flask

Question 5

What is the purpose of the rubber neck around the thermometer?

Answer 5

To prevent loss of gas

Question 6

What is the purpose of adding antibumping granules to the flask in distillation?

Answer 6

To ensure smooth boiling with no bumps

Question 7

What is reflux?

Answer 7

A technique used to stop reaction mixtures boiling away into the air

Question 8

Draw reflux diagram

Answer 8

See notes!!

Question 9

Briefly describe how you would prepare and purify an organic liquid

Answer 9

1. use a separating funnel to separate organic layer and aqueous layer
2. use an anhydrous salt (e.g. CaCl2) as a drying agent to dry organic product
3. redistill if necessary to purify further

Question 10

Why can a separating funnel not be used to separate ethanol and water?

Answer 10

They are miscible - they mix together to form one homogenous solution, completely dissolving together since they are both polar

Question 11

Why must the tops of drying agents like MgSO4 always be put on when not being used?

Answer 11

MgSO4 absorbs moisture from air which will hydrate it, making it less effective as a drying agent