RP5 - Distillation of a product from a reaction

Question 1

How is Cyclohexene formed?

Answer 1

From the dehydration of Cyclohexanol

Question 2

Draw the displayed formula to show this reaction

Answer 2

Cyclohexanol –> Cyclohexene + water

Question 3

What is required for this reaction to take place?

Answer 3

Concentrated Phosphoric acid and heat

Question 4

Describe how you would carry out the dehydration of cyclohexanol?

Answer 4

1. place 10cm3 of cyclohexanol into a pear shaped flask, that has been weighed. Reweigh the flask and record the mass of cyclohexanol
   2) in a fume cupboard, holding the flask with a clamp and pointing the flask towards the back of the fume cupboard, carefully add
2. set up distillation apparatus and add anti-bumping granules
3. Heat the flask very slowly and gently, collecting the liquid that distils between 70-90’. Do not let the flask boil dry

Question 5

Purification of Cyclohexene. Describe the steps?

Answer 5

5. The distillate will be a mixture of mainly cyclohexene and water, together with impurities such as unreacted cyclohexanol. Pour this mixture into a separating funnel
6. Add an equal volume of sodium chloride to help separate the organic and aqueous layers. Stopper the funnel and shake before allowing the layer to settle.
7. Run of the aqueous layer into a beaker, and then collect the organic layer in a smaller beaker
8. Add 2/3 small pieces of anhydrous calcium chloride, a drying agent, and stopper the flask. Shake for a few minutes until the liquid is clear
9. Decant the alkene into a clean flask that has been weighed and redistil it between 81-85’
10. Fine the mass of your product
11. Now we can use bromine water to test that the product is unsaturated.

Question 6

Why are Anti-bumping granules used?

Answer 6

Anti-bumping granules prevent large bubbles from forming and ensure that the liquid doesn’t boil too vigorously as this would result in the mixture boiling over into the condenser and undesired impurities would contaminating the product.

Question 7

Why is sodium chloride used?

Answer 7

Acts as a drying agent

Question 8

Why do we run off the aqueous layer and keep the organic layer?

Answer 8

this removes the water, little cyclohexanol and water

Question 9

Why is Calcium chloride used?

Answer 9

Used as a drying agent to remove water in order for pure distillation to take place

Question 10

If flammable substances are present what must be used?

Answer 10

A electric heater or water bath

Question 11

Where should the thermometer go?

Answer 11

The bulb of the thermometer should be at the T junction connecting to the condenser to measure the correct boiling point

Question 12

Why does water have to enter through the condenser at the lowest point and leave at the highest point?

Answer 12

The water must enter at the lowest point and leave at the highest point to go against gravity as this ensures that water fills the
condenser (prevents backflow of water), maximising heat transfer for condensation (more efficient cooling).

Question 13

Why must the flask not be sealed?

Answer 13

The collection flask must not be sealed to the condenser, the system should not be air tight because as it is heated the air inside the system expands. If it is air tight then the air cannot escape and may cause the apparatus to crack

Question 14

NEXT

Question 15

Preparation of Ethanol from Oxidation and Distillation of Ethanol

Question 16

Describe the method used for this reaction

Answer 16

1. Make the oxidising agent by dissolving potassium dichromate (VI) in dilute sulfuric acid. The concentration of the potassium dichromate(VI) should be approximately 1 g in every 10 cm3 of this dilute acid.
2. Using a 25 cm3 measuring cylinder, carefully measure out 12 cm3 of the acidified potassium dichromate(VI) solution and pour this into a boiling tube.
3. Cool the boiling tube in a beaker of cold water. Keep the test tube cool to avoid loss of
   the volatile ethanal.
4. Using a 10 cm3 measuring cylinder, carefully measure out 2 cm3 of ethanol.
5. Using a teat pipette, slowly add the 2 cm3
   of ethanol dropwise, to the oxidising agent in the cooled boiling tube, shaking the tube gently to mix the contents.
6. Add a few anti-bumping granules to the boiling tube and attach to it a bung fitted with a right-angled glass delivery tube.
7. Clamp the boiling tube at about 450 in a beaker of water so that the delivery tube goes to a test tube which is immersed in cold water in a beaker. Keep the test tube cool to avoid loss of the volatile ethanal.
8. Gently heat the beaker of water containing the ethanol to slowly distil off approximately 5 cm3 of liquid distillate.
9. Use Tollen’s reagent to test the distillate for ethanal. (Should produce a silver
   mirror).

Question 17

Draw a diagram of distillation

Question 18

FINISHED