Practical 5 - Synthesis of a liquid organic product

Question 1

Aim

Answer 1

To synthesise 2-chloro-2-methy|propane using 2-methylpropan-2-ol and concentrated hydrochloric acid and purify the product using a separating funnel followed by distillation

Question 2

How do we know which layer is the aqueous layer?

Answer 2

When adding deionised water, this is the layer that increases in volume

Question 3

Method

Answer 3

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1. Add 30 cm of concentrated HCI solution to a stoppered conical flask. This step should be performed in a fume cupboard.
2. Cool the HCl solution in the ice bath.
3. When the HCl solution has cooled add 2.5 g anhydrous CaCl to the solution.
4. Add 10 cm of (CH)3COH to the reaction mixture and mix thoroughly.
5. Remove the mixture from the ice bath and allow it to slowly warm up to room temperature. Note that a gaseous side product can be formed at this stage and so the stopper should be released periodically to alleviate any build-up of pressure.
6. Transfer the reaction mixture to the separating funnel.
7. Stopper the funnel and invert it a few times to thoroughly mix the reaction mixture. You may need to alleviate the pressure in the funnel by holding it upside down and opening the tap.
8. Run off and discard the aqueous layer. If you are unsure which layer is the aqueous layer, add deionised water to funnel and see which layer increases in volume.
9. Add 10 cm of saturated NaHCO, solution to the organic layer and mix thoroughly in the separating funnel. COz gas is formed in this step so it is important to alleviate the pressure in the funnel periodically.
10. Run off and discard the aqueous layer.
11. Repeat steps 9 and 10 to wash the product for the second time.
12. Repeat steps 9 and 10 using 15 cm of deionised water to wash the product for a third time

13. Transfer the organic product to a conical flask, add anhydrous MgSO4 and swirl vigorously. Keep adding MgSO4 until it no longer clumps together.
14. Transfer the organic product to the round bottomed flask through a filter funnel with a plug of cotton wool to remove the MgSO4.
15. Set up the distillation apparatus.
16. Distil off the (CHs)s CCI produced and collect in a clean, dry, pre-weighed 100 cm?
    conical flask.
17. Record the temperature at which the liquid product is collected.
18. Calculate the mass of the product and use this information to calculate the product yield
    (Note that the density of (CH)COH is 0.775 g cm 3)