16.1 Practical techniques in organic chemistry

Question 1

Quickfit apparatus

Answer 1

Round-bottom or pear-shaped flask
Receiver
Screw-tap adaptor
Condenser
Still head

Question 2

Apparatus to heat under reflux

Answer 2

Round-bottom or pear-shaped flask
Condenser
Rubber tubig
Stand and clamp
Heat source

Question 3

When heating flammable liquids what can be used

Answer 3

A heating mantle so there is no naked flame present

Question 4

What can be used for a reaction below 100 degrees

Answer 4

A water bath

Question 5

How to set up apparatus

Answer 5

Flask clamped by neck
Add reaction mixture and anti-bumping granules
Apply thin layer of grease to ground-glass joint on condenser
During reflux, condenser kept in upright position
Rubber tubing to connect inlet of condenser to tap and outlet to sink

Question 6

Why must anti-bumping granules be added

Answer 6

Contents boil smoothly

If not used, large bubbles at bottom of liquid make glassware vibrate or jump violently

Question 7

Distillation

Answer 7

Once reflux is complete, crude liquid or solid product needs to be purified to remove any by-products and remaining reactants

Question 8

What is distillation

Answer 8

Common method used to separate a pure liquid from its impurities

Question 9

Apparatus to carry out a distillation

Answer 9

Round-bottom or pear-shaped flask
Condenser
Rubber tubing
Heat source
Stand and clamp
Screw-cap adaptor
Receiver adaptor
Still head
Thermometer

Question 10

What is an easy way to identify the organic layer

Answer 10

Add some water

The layer that gets bigger is the aqueous layer

Question 11

Separating the organic layer

Answer 11

Separate using separating funnel

1. Ensure that tap of separating funnel is closed
2. Pour mixture of liquids into separating funnel, place stopper in top of the funnel and invert to mix contents
3. Allow layers to settle
4. Add some water to see which layer increases in volume - this is the aqueous layer
5. Place conical flask under separating funnel, remove stopper and open tap until whole of lower layer has left funnel
6. Place second conical flask under separating funnel to collect other later

Can remove impurities by adding aqueous sodium carbonate and shaking
Any acid present will react releasing CO2

Question 12

Drying the organic product

Answer 12

Traces of water removed by adding drying agent (an anhydrous inorganic salt)

1. Add organic liquid to conical flask
2. Using spatula, add some of drying agent to liquid and gently swirl contents to mix together.
3. Place a stopper on flask to prevent product from evaporating away. Leave for about 10 mins
4. If solid has stuck together in lump, still some water present. Add more drying agent until some solid dispersed in solution as fine powder
5. Decant the liquid from the solid into another flask, if liquid is dry, it should be clear