Core Practical 6 Lab

Investigating chlorination of 2-methylpropan-2-ol

Aim

To produce and purify a sample of 2-chloro-2-methylpropane

These videos & activities will support your laboratory work and help you with the analysis of your results

Preparation of 2-chloro-2-methylpropane

Lesson 2 ALCOHOLS Audio NJM.pptx

Procedure

1. Pour 10 cm3 of 2-methylpropan-2-ol and 35 cm3 of concentrated hydrochloric acid into a large conical flask. Swirl the contents of the flask very gently.

2. Place the bung in the mouth of the flask. Gently swirl again, then remove the bung to release the pressure.

3. Continue swirling the mixture with the bung fitted and then releasing the pressure for around 20 minutes. There should be two layers in the flask. The upper layer is the crude product.

4. Add approximately 6 g of powdered anhydrous calcium chloride to the flask and swirl until it has dissolved. This ensures that any unreacted alcohol is in the lower aqueous layer.

5. Transfer the reaction mixture to a separating funnel. Allow the mixture to settle into the two layers. Run off and discard the lower layer. Retain the upper organic layer in the separating funnel.

6. Add approximately 20 cm3 of sodium hydrogencarbonate solution to the separating funnel. Swirl the funnel and remove the bung to release the pressure, caused by the production of carbon dioxide, at frequent intervals. Run off and discard the lower aqueous layer.

7. Repeat the washing with sodium hydrogencarbonate, shake the separating funnel and release the carbon dioxide gas produced, at frequent intervals.

8. Run off and discard the lower layer. Ensure none of the aqueous layer remains in the tap.

9. Run off the organic layer into a small conical flask. Add a spatula full of anhydrous sodium sulfate. Place the bung in the flask and swirl the contents to mix. Leave the mixture until the liquid looks completely clear, swirling occasionally.

10. Decant the organic liquid into a 50 cm3 pear-shaped (or round-bottomed) flask

11. Set the flask up for distillation, as shown in the diagram below.

12. Collect the fraction boiling between 50 °C and 52 °C.

13. Place your pure product in a labelled sample tube

Things to consider CPAC 1a

CPAC 1a - Correctly follows instructions to carry out the experimental techniques or procedures

· Carry out reaction in a conical flask as per instructions with no/little prompting

· Carry out washes in the separating funnel as per instructions with no/little prompting

· Prepare apparatus for distillation:

1. Set up apparatus with minimum help ensuring seals

2. Water in and out correctly set up

3. Thermometer in correct place

4. Collection flask

· Carry out distillation:

1. Controls heat to flask

2. Water flowing

3. Collect product over correct temperature range

4. Store and label sample correctly

Things to consider CPAC 2a

CPAC 2a- Correctly uses appropriate instrumentation, apparatus and materials to carry out investigative activities, experimental techniques and procedures with minimal assistance or prompting.

· Select the correct equipment as per instructions

· Correctly isolate layers using a separating funnel

· Carry out wash steps in correct order in separating funnel

Things to consider CPAC 2b

CPAC 2b - Carries out techniques or procedures methodically, in sequence and in combination, identifying practical issues and making adjustments when necessary.

· Release gas from separating funnel

· Confidently set up distillation apparatus as in diagram with minimal / no assistance

· Water into condenser at bottom and out at top

· Add anti bumping granules

· Use gas tap to control distillation heat

· Bulb of thermometer at correct junction

· Collect product over correct temperature range

· Use a thermometer to measure temperature to a degree

Testing your product

Perform the following test on the distillate:

Place a few drops of the distillate into a test tube.

Add 5 cm3 of ethanol and 1 cm3 of aqueous sodium hydroxide to the test tube.

Warm the mixture in a water bath.

Add excess nitric acid to the mixture followed by a few drops of silver nitrate solution.

Equipment

large 250 cm3 conical flask with bung ● 100 cm3 (or larger) separating funnel with bung ● 250 cm3 beaker for liquid run out of separating funnel ● filter funnel to fit separating funnel ● apparatus for distillation with 50 cm3 pear-shaped (or round-bottomed) flask and thermometer able to read up to 100 °C ● 25 cm3 and 100 cm3 measuring cylinders ● 2-methylpropan-2-ol ● sodium hydrogencarbonate solution ● 6 g powdered anhydrous calcium chloride ● anhydrous sodium sulfate ● small conical flasks with bungs ● sample tube ● silver nitrate solution ● dilute sodium hydroxide solution ● dilute nitric acid ● 70 cm3 concentrated hydrochloric acid ● test tubes ● spatulas ● 5 cm3 ethanol ● Bunsen burner

Learning Tip

The –OH group in an alcohol can be replaced by a halogen. PCl5 can be used to make a chloroalkane, HBr (which is made in situ) can be used to make a bromoalkane, and red phosphorus with iodine can be used to make an iodoalkane.
The purity of a substance can be checked by measuring its boiling temperature

Understanding How to Stay Safe

Hazcards COSHH

Read the Hazcards COSHH information for the chemicals used in the practical so that you are aware of how to keep yourself and others safe 84B,19B,98B,87,91A,67,47A

Wear goggles and gloves.
2-methylpropan-2-ol is flammable and harmful.
Concentrated hydrochloric acid is corrosive and the hydrogen chloride fumes it produces are toxic and corrosive. Carry out this practical in a fume cupboard or well-ventilated room.
2-chloro-2-methylpropane is flammable.
Calcium chloride is an irritant.

Things to consider CPAC 3b

CPAC 3b - Uses appropriate safety equipment and approaches to minimise risks with minimal prompting.

· Collect all eqpt at start to minimise walking around the lab once practical work

· Set up work space in an organised, tidy & safe fashion

· No spillages/deals with spillages appropriately with minimal fuss

· Keep stoppers on bottles when not in use

· Discuss medical issues prior to practical work that may need considering (ie asthmatic/ epileptic…)

· Correct disposal of reaction mixture (reagents & products) at end of practical

· Area cleared away properly & cleaned down (if needed) for following students without prompting

· Set up distillation apparatus with secure joints to ensure no leaks

· Clamp apparatus appropriately

· Control heat to condenser to avoid gases escaping

· Use of water bath to heat pear shaped flask

· Wear safety goggles, gloves & lab coat throughout

Required Resources

AS-and-A-level-Chemistry-Core-Practical-6 - Student worksheets.docx

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Consult CLEAPSS Hazcards® 84B,19B,98B,87,91A,67,47A. Perform a risk assessment using up-to-date information before this practical is carried out

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