Practical Techniques - Organic Synthesis

Question 1

In distillation, why is it necessary to have continuous water flow around the condenser?

Answer 1

So that the water remains cool and the mixture is cooled and condensed.

Question 2

Name 3 drying agents.

Answer 2

Calcium chloride, CaCl2
Calcium sulfate, CaSO4
Magnesium sulfate, MgSO4

Question 3

Describe a method that can be used to separate organic liquids.

Answer 3

1. Add mixture to a separating funnel.
2. Add distilled water to the mixture and see which layer gets larger to identify the aqueous layer.
3. Run the aqueous layer out of separation funnel and organic layer into a conical flask.
4. Add CaCl2 drying agent and decant to obtain pure organic sample.
5. Redistillation. Set up distillation apparatus. Add mixture to round-bottom flask and heat to separate one product into conical flask and the other product in the starting vessel.

Question 4

How is a drying agent used?

Answer 4

1. Add drying agent to liquid and swirl to mix contents.
2. Place stopper on flask to prevent product evaporating away. Leave for 10 minutes.
3. If solid is lumped together, add more drying agent until solid disperses.
4. Decant liquid into another flask.

Question 5

What are the 5 pieces of Quickfit apparatus?

Answer 5

Round-bottom flask
Receiver
Screw-tap adaptor
Condenser
Still head

Question 6

Why are some chemicals heated under reflux?

Answer 6

To prevent volatile organic products from escaping the flask and boiling away.

Question 7

What is distillation used for?

Answer 7

It separates pure liquid from its impurities by boiling the liquid into a separate conical flask.

Question 8

What happens in reflux?

Answer 8

Set up apparatus.

Reacting mixture is placed into round-bottom flask and anti-bumping granules are added to ensure contents boil smoothly.

Contents are heated using a heating mantle. Liquid continually boils into condenser where it is cooled back down into round-bottom flask.

Question 9

How is water supplied to the condenser in reflux and distillation?

Answer 9

Cold water travels through rubber tubing from the tap into the condenser.

Question 10

What happens in distillation?

Answer 10

Set up apparatus.

Reacting mixture is placed into flask and is heated with bunsen burner.

Liquid with lower boiling point will boil into condenser, where it will cool back into liquid and will drip into a collecting flask.