Chapter 16 Organic Synthesis

Question 1

How can you remove an organic layer from an aqueous layer? Give the 7 step method

Answer 1

Use a separating funnel

1. Ensure that the tap of the separating funnel is closed
2. Pour the mixture of liquids into the separating funnel, place a stopper in the top of the funnel and invert to mix the contents
3. Allow the layers to settle
4. Add some water to see which layer increases in volume- this is the aqueous layer
5. Place a conical flask under the separating funnel, remove the stopper and open the tap until the whole of the lower layer has left the funnel
6. Place a second conical flask under the separating funnel to collect the other layer
7. You will now have one conical flask containing the organic layer and another containing the aqueous layer. Label the flasks so you don’t get confused

Question 2

What three ways can an organic liquid be prepared an purified?

Answer 2

1. Using a separating funnel
2. Drying with an anhydrous salt
3. Redistillation

Question 3

How can an organic product be dried with an anhydrous salt. Give the 5 step method

Answer 3

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

Question 4

What is redistillation and how is it used?

Answer 4

Sometimes organic liquids have similar boiling points so your prepared solution may still contain some impurities. The distillation apparatus is cleaned and dried and set up again for a second distillation. This time you only collect the product with the boiling point of the compound you are looking for. The narrower the boiling point range, the purer the product.

Question 5

What is quickfit apparatus and what is it used for?

Answer 5

Quickfit apparatus contains:

• Round-bottom or pear-shaped flask
• receiver
• screw-tap adaptor
• condenser
• still head

It can be used for distillation and heating under reflux

Question 6

What is the functional group of an aldehyde?

Answer 6

-CHO

• C = O
  |
  H

Question 7

What is the functional group of a carboxylic acid?

Answer 7

-COOH

• C = O
  |
  OH

Question 8

What is the functional group of an Ester?

Answer 8

-COOC-

• C = O
  |
  O — C

Question 9

What is the functional group of a ketone?

Answer 9

-CO

      O
       | C — C — C

Question 10

How can you devise two stage synthetic routes?

Answer 10

1. Identify the functional groups in your starting and target molecules
2. Identify the intermediate that links the two
3. State the reagents and conditions for each step