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Aim
Aim
To investigate the relative rates of hydrolysis of primary, secondary and tertiary halogenoalkanes and of chloro-, bromo-, and iodoalkanes
To investigate the relative rates of hydrolysis of primary, secondary and tertiary halogenoalkanes and of chloro-, bromo-, and iodoalkanes
These videos & activities will support your laboratory work and help you with the analysis of your results
These videos & activities will support your laboratory work and help you with the analysis of your results
Equipment
Equipment
250 cm3 beaker ● 12 test tubes with bungs ● 1-chlorobutane ● 1-bromobutane ● 1-iodobutane ● 2-bromobutane ● 2-bromo-2-methylpropane ● silver nitrate solution ● 15 cm3 ethanol ● dropping pipettes ● two 10 cm3 measuring cylinder ● stop clock ● labels for test tubes ● kettle
Procedure
Procedure
Part 1
1. Set up a water bath. Fill the 250 ml beaker up to the three quarters mark with water, at around 50 °C.
2. Fill three test tubes each with 5 cm3 of ethanol. Now add four drops of 1-iodobutane to the first tube, four drops of 1-bromobutane to the second tube and four drops of 1-chlorobutane to the third tube. Label the tubes.
3. Loosely place a bung in each test tube and place the test tubes in the water bath.
4. Pour 5 cm3 of silver nitrate solution into three clean test tubes. Now place the test tubes in the water bath.
5. When the halogenoalkane–ethanol solutions have reached the temperature of the water bath, add the silver nitrate solution to one of the halogenoalkane–ethanol solutions and replace the bung. Start the stop clock as you do so.
6. Measure the time taken for the precipitate to appear. As soon as the solution becomes cloudy stop the stop clock.
7. Repeat steps 5 and 6 for the other two halogenoalkanes.
Part 2
8. Repeat Part 1 using 1-bromobutane, 2- bromobutane and 2-bromo-2-methylpropane instead of the other halogenoalkanes.
Things to consider CPAC 1a
Things to consider CPAC 1a
Correctly follows instructions to carry out the experimental techniques or procedures.
Things to consider CPAC 2b
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.
· Choose equipment independently
· Plan & organise to ensure timings will be accurate - explain how you will:
o Place equipment on a suitable surface for precipitate to be clearly seen
o Maintain planned temperature – use water bath & allow time for solutions to reach a stable temperature
o Good team work for timing and mixing solutions
Things to consider CPAC 2c
Things to consider CPAC 2c
CPAC 2c – Identifies and controls significant quantitative variables where applicable, and plans approaches to take account of variables that cannot readily be controlled.
· Use a thermometer to correctly measure temperature to a degree.
· Place the thermometer in the solutions to test temperatures not in the water surrounding
· Allow solutions to reach temperature before mixing
· Clean the thermometer between the solutions to avoid contamination
· Work together to ensure the timer is started when the reactants are mixed
Learning Tips
Learning Tips
The hydrolysis of halogenoalkanes is a nucleophilic substitution reaction.
In this investigation the nucleophile is water.
If NaOH is used to hydrolyse the halogenoalkanes, then any excess NaOH has to be neutralised by HNO3 before adding AgNO3
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 44A,44B,87
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 44A,44B,87
Wear eye protection.
Halogenoalkanes are flammable and harmful.
Ethanol is flammable.
Silver nitrate is corrosive.
Obtain hot water from a kettle rather than using a naked flame in the laboratory.
Things to consider CPAC 3b
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 fashion
· Keep work space tidy and organised
· Wear safety goggles, lab coat, throughout
· No spillages/deal with spillages appropriately with minimal fuss
· Keep stoppers on bottles when not in use
· Hold test tubes in racks (to prevent rolling off the table & smashing)
· Stand test tubes in appropriate sized beaker to stabilize (which may be clamped to increase stability)
· 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 without prompting
Required Resources
Required Resources
AS-and-A-level-Chemistry-Core-Practical-4-Student Worksheets.docxConsult CLEAPSS Hazcards® 44A,44B,87. Perform a risk assessment using up-to-date information before this practical is carried out
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