Chapter 16 - Organic Synthesis

Question 1

What equipment is necessary to heat under reflux?

Answer 1

Pear shaped flask
Condenser
Rubber tubing
Stand and clamp
Heat source (bunsen burner, tripod and gauze OR heating mantle)

Question 2

Which method of heating is used when heating flammable liquids?

Answer 2

Heating mantle so there is no naked flame.

Question 3

What is the purpose of heating under reflux?

Answer 3

Enables a liquid to be continually boiled whilst the reaction takes place. Prevents volatile components from escaping and the flask from boiling dry.

Question 4

What is the equipment necessary for distillation?

Answer 4

Pear shaped flask
Condenser
Rubber tubing
Heat source
Stand and clamp
Screw cap adaptor
Receiver adaptor
Still head
Thermometer

Question 5

What is the purpose of distillation?

Answer 5

Separate a pure liquid from its impurities.

Question 6

How is an organic product purified?

Answer 6

Ensure the tap of the separating funnel is closed,
Pour the mixture of liquids, place a stopper in the top and invert to mix,
Allow the layers to settle.
Add some water to see which layer will increase in volume (aqueous layer)
Place a conical flask undeneath, remove the stopper and open the tap until the lower layer has left.
Place a second flask underneath to collect the organic layer

Question 7

How can acid impurities be removed?

Answer 7

Adding aqueous sodium carbonate and shaking the mixture in the seperating funnel.
Carbon dioxide gas is made and must be released via the tap (funnel upside down).
Aqueous sodium carbonate layer is then removed and organic layer washed with water.

Question 8

How can water be removed from organic products?

Answer 8

A drying agent is added (typically an anhydrous inorganic salt) and then mixed,
Place a stopper on the flask,
Leave for ten minutes,
If the solid is stuck together in a limp, there is still some water present. Add more until some solid is dispersed as a fine powder,
Decant liquid into another flask.

Question 9

What is a target molecule?

Answer 9

The compound that is being prepared by organic synthesis.

Question 10

How would an aldehyde be formed from a halogenoalkane?

Answer 10

Stage 1: Add NaOH under reflux to form an alcohol

Stage 2: Oxidise with acidified potassium dichromate under gentle heat and distill off

Question 11

How would a ketone be formed from an alkene?

Answer 11

Stage 1: Add steam with acid catalyst to form an alcohol

Stage 2: Oxidise with acidified potassium dichromate under reflux

Question 12

What is ozonolysis?

Answer 12

A technique used to break open a C=C double bond. Useful for the preparation of aldehydes and ketones.

Question 13

what are the three common drying agents?

Answer 13

anhydrous calcium chloride, CaCl2 (drying hydrocarbons)
anhydrous calcium sulfate, CaSO4
anhydrous magnesium sulfate, MgSO4

Question 14

Describe the process of purifying organic products

Answer 14

1) Add rxn mixture to separating funnel
2) place a stopper and invert to mix content
3) Add distilled water allow layers to spectate - layer that increases in V is the aqueous later. This happens because the organic layer has higher density than the aqueous layer.
4) place a concical flask under separating funnel, remove the stopper and open tap to allow organic layer to run and collect.
5) place a second funnel under the separating funnel to collect the other layer
6) label the flasks

Question 15

reaction may use acid to react, and thus my result in acid impurity. Describe the process of removing the impurity.

Answer 15

add aqueous sodium carbonate to spreading funnel

Then shake the mixture.

Any acid present will react with the sodium carbonate releasing carbon dioxide gas.

Question 16

Describe the process of drying the organic product

Answer 16

1) add 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 minutes.
4) if the solid has all stick together in a lump, there is still some water present. Add more drying agent until some of the solid is dispersed in the solution as a fine powder.
5) decant the liquid from the solid into another flask.

Question 17

Add pic

Answer 17

can’t distill - bpt too close together
if heated to 100•c, some of the organic liquid would also evaporate.

1) Add rxn mixture to separating funnel
2) add sodium carbonate to remove any acid impurities
3) add distilled water and allow alters to spectate - layer that increases in V is the aqueous layer.
4) open tap, allow organic layer to run out and collect using conical flask

Now chances are there is still some traces of water left in the organic layer

6) add a small amount of drying agent to organic layer - they absorb the water left
7) filter/decant

Question 18

React ozone with but-2-new

Answer 18

Ozonolysis

But-2-ene + O3 + H20&raquo_space;> 2 H3CCH=O + H20