Unit 6 – Synthesising Organic Compounds
Practical 2
Hydrolysis of Bromoethane to Ethanol
Primary halogenoalkane can be hydrolysed to form alcohols. The reaction occurs
when the halogenoalkane is refluxed with hydroxide ions (OH-)
Halogenoalkanes are compounds containing a halogen atom (fluorine, chlorine,
bromine or iodine) joined to one or more carbon atoms in a chain.
Halogenoalkanes are insoluble in water so the solvent is usually ethanol/water mix. If
water was used as the solvent, the halogenoalkane and the sodium hydroxide solution
wouldn't mix and the reaction could only happen where the two layers met.
Nucleophilic Substitution reaction.


A nucleophile is an the electron rich species that will react with an electron
poor species
A substitution implies that one group replaces another.
Reaction
CH3CH2Br
+
Bromoethane +
NaOH
CH3CH2OH
+
NaBr
Sodium Hyrdoxide
Ethanol
+
Sodium
Bromide
Preparation

Make sure that your lab coat is fully fastened at all times.

Make sure you wear gloves and safety goggles at all times.

This experiment should be carried out in the fumehood at all times.
Part one- Hydrolysis of bromoethane to ethanol
1.
Place 25mls of bromoethane into a round-bottomed Quickfit flask

2.
Measure the bromoethane inside the fumehood.
Add 25mls of 0.1M sodium hydroxide and a few pieces of anti-bump
granules in to the round-bottomed Quickfit flask.
3.

Measure the sodium hydroxide inside the fumehood.

Swirl the flask gently to mix the reagents.
Set up the Quickfit apparatus for refluxing as shown below. Instead of a
Bunsen burner use the heating mantle. Turn on the water to run through
the condenser.

The water should come in at the bottom of the condenser and out at the
top of the condenser.
4.
Heat the solution under reflux to 70°C for 15 mins.

Set the heating mantel to number 7.
Rearrange the apparatus for distillation (as shown below – use the heating
5.
mantle instead of the Bunsen burner).
6.
Distil off the ethanol produced and collect in a clean, dry 100ml conical
flask.

Ethanol will be the first product to be distilled.

Remember to record the temperature you start to collect liquid at.

You can stop the distillation when the temperature begins to rise again.
Part two – Test your product.
1.
Record the temperature you started to distil a liquid at.
2.
Record the volume of liquid distilled.
3.
Take 3ml of your sample and place it into a clean boiling tube
4.
Attach the boiling tube to the retort stand as shown overleaf.
le
Thermometer
Retort Stand
Boiling Tube
Water
Sample of
Ethanol
Apply Heat
5.
Allow the ethanol to boil.
6.
Record the temperature on the thermometer after the solution has begun to
boil.

This will be the temperature of the ethanol vapour
Results
1.
o
Boiling point of your product =
C
Bromoethane + Sodium Hydroxide
Ethanol
+ Hydrobromic
acid
1 mole
1 mole
1 mole
RMM of 1 mole of Bromoethane = 109 g
1 mole
RMM of 1 mole of Ethanol = 46g
Density of Bromoethane = 1.47 g/cm3, therefore in 1 cm3 of bromoethane =
1.47.g.
Equation 1 – Determine the number of moles of bromoethane used in the
reaction.
Moles of bromoethane used in this reaction =
Grams of bromoethane in 25cm3
RMM of 1 mole of bromoethane
=
moles
In a 1:1 reaction the number of moles of bromoethane used = number of moles of
ethanol produced.
Equation 2 - Determine the mass of ethanol produced.
Mass of ethanol
= No. of moles of ethanol produced X RMM of 1 mole
-
of ethanol
=
g
Equation 3 – Determine the percentage yield of product.
Density of Ethanol = 0.76g/cm3
Volume of product
= Density of 1cm3 of ethanol X mass (equation 2)
=
cm3
% Yield
=
Actual Yield Volume
Volume of product
=
%
Questions.
1. Is the % yield more or less than 100%? Explain your results.
2. Why is broken porcelain added to the solution before reflux?
o
3. The actual boiling point of ethanol is 78.3 C, does this correspond to the
temperature at which you distilled your product?? What would cause the
liquid to be distilled at a different temperature?