Experiment O03 Chemical properties of ethanol
Chemicals:
A.
Universal indicator, (3 drops)
Ethanol. (1 cm3)
B.
1 M H2SO4, (10 cm3)
Solid sodium dichromate(VI), Na2Cr2O7, (3 g)
Anti-bumping granules, (2)
Ethanol, (5 cm3)
Fehling's solution 1, (1 cm3)
Fehling's solution 2, (1 cm3)
2 M NaOH, (1 drop)
0.05 M AgNO3, (5 cm3)
2 M ammonia solution. (~1 cm3)
C.
1 M H2SO4, (10 cm3)
Solid sodium dichromate(VI), Na2Cr2O7, (5g)
Concentrated H2SO4, (2 cm3)
Anti-bumping granules, (3)
Ethanol, (1 cm3)
Universal indicator papers,
Anhydrous sodium carbonate. Na2CO3, (1g)
D.
Ethanol, (5 drops)
Iodine solution (10% I2 in KI solution), (1 cm3)
2 M NaOH. (~10 cm3)
E.
Ethanol, (1 cm3)
Sodium. (small pieces under oil)
F.
Ethanol, (2 cm3)
Glacial ethanoic acid, (1 cm3)
Conc.H2SO4, (3 drops)
1 M Na2CO3. (10 cm3)
G.
Ethanol, (2 cm3)
Pumice stone, (4-8 mesh)
Bromine water, (2 drops)
Acidified 0.01 M KMnO4. (2 drops)
P.1
Experiment O03 Chemical properties of ethanol
Apparatus:
A. Safety spectacles,
Test-tube.
B. Safety spectacles,
Protective gloves,
Ground-glass-joint apparatus in fig.1
10 cm3 measuring cylinder,
Spatula and 3 teat-pipettes,
Small funnel, wide stem.
C.
Safety spectacles,
Protective gloves,
Ground-glass-joint apparatus in fig.1
Measuring cylinder, 10 cm3,
Spatula and teat-pipette,
Small funnel, wide stem.
D.
Safety spectacles,
2 teat-pipettes,.
E.
Safety spectacles,
Forceps,
Filter paper,
Splint,
Watch glass.
F.
Safety spectacles,
Teat-pipette (1).
G.
Safety spectacles,
3 test-tubes with corks,
Ceramic wool,
Teat pipette (1),
Delivery tubes and bungs as in Fig.3
Water trough.
P.2
Experiment O03 Chemical properties of ethanol
Aim
The purpose of this experiment is to study some of the reaction of ethanol, a typical primary
alcohol.
Introduction
The reactions to be investigated, with approximate times required, are:
A.
Solubility in water
Individual
5 minutes
B.
Mild oxidation
Group 1&2
30 minutes
C.
Further oxidation
Group 3&4
40 minutes
D.
Triiodomethane reaction
Individual
5 minutes
E.
Reaction with sodium
Individual
5 minutes
F.
Esterification
Individual
5 minutes
G.
Dehydration
Group 5
30 minutes
Your teacher may want you to divide up the experiment among a group, with each member
reporting back on two parts.
You will use Fehling's solution in some of your tests.
This solution contains a blue copper(II) compound which, in the presence of a reducing agent,
changes to a red copper(I) compound.
Cu2+ + e-  Cu+  Cu2O
Blue
Red
You will also use an ammoniacal solution of silver oxide (Tollen's reagent) which, in the
presence of a reducing agent, produces a 'silver mirror' (and/or a grey ppt):
Ag+ + e-  Ag(s) Silver mirror
Each of these tests confirms the presence of a reducing agent.
Hazard warning
1.
Ethanol is very flammable.
2.
Bromine and glacial ethanoic acid have dangerous fumes and burn the skin.
3.
Concentrated sulphuric acid is very corrosive and reacts violently with water.
4.
Tollens' reagent for the silver mirror test becomes explosive if dry.
5.
Sodium is extremely dangerous.
6.
Sodium dichromate(VI) is a powerful oxidant and can damage the skin.
P.3
Experiment O03 Chemical properties of ethanol
Procedure:
A.
1.
Solubility in water
Pour about 1 cm3 of distilled water into a test-tube, add a few drops of universal indicator
and shake gently.
2.
Add about 1 cm3 of ethanol and shake the mixture. Note, in the Results Table, whether the
addition of ethanol has any effect on the colour of universal indicator. (Your distilled water
may be weakly acidic due to the absorption of atmospheric carbon dioxide.)
B.
1.
Mild oxidation
Into a pear-shaped flask, pour 10 cm3 of 1 M sulphuric acid. Using a small wide-stemmed
funnel, add 3.0 g of sodium dichromate(VI) and 2-3 anti-bumping granules.
2.
Swirl the flask gently until all the sodium dichromate(VI) has dissolved.
3.
Slowly add 5 cm3 of ethanol and swirl to mix.
4.
Set up the apparatus shown in figure 1. Ensure that water enters the condenser from the
bottom and leaves at the top.
Fig. 1
Distillation
3
5.
Heat very gently until 2-3 cm of liquid has distilled over.
6.
Keep the distillate and test it in the following ways:
(a) Smell cautiously (compare with ethanol).
(b) Transfer about 1 cm3 of the distillate to a test-tube. Add about 1 cm3 of Fehling's
solution 1 followed by 1 cm3 of Fehling's solution 2. Boil gently. Note your
observations in the Results Table.
(c) Pour about 5 cm3 of 0.05 M silver nitrate solution into a boiling-tube. Add one drop of
sodium hydroxide solution. Drop by drop, add aqueous ammonia until the precipitate
disappears. Add 2-3 drops of the distillate and warm the tube in a beaker containing hot
water. Note your observations. (This is called the 'silver mirror test' or the 'Tollens test')
(Do not keep this solution -- It becomes explosive on evaporation.)
P.4
Experiment O03 Chemical properties of ethanol
C.
Further oxidation
1.
Into a pear-shaped flask, pour 10 cm3 of 1M sulphuric acid. Through a wide-stemmed
funnel add 5 g of sodium dichromate(VI) and 2 or 3 anti-bumping granules.
2.
Swirl the flask gently until all the sodium dichromate(VI) has dissolved.
3.
With care, add 2 cm3 concentrated sulphuric acid.
4.
Cool the flask under a running tap.
5.
Set up the apparatus shown in figure 2, (preferably in a fumecupboard.)
Fig. 2
Heating under reflux
6.
Drop by drop, add 1 cm3 of ethanol down the condenser.
7.
Boil gently under reflux for 20 minutes. (While you are waiting you could do reactions D, E
and F.)
8.
Rearrange your equipment so it is set up as in Figure 1 above.
9.
Distil 2-3 cm3 of liquid.
10. Test the distillate as follows, and note yor observations.
(a) Smell cautiously (compare with ethanol).
(b) Add a drop to moistened universal indicator paper,
(c) Add a few drops to about 1 g of solid sodium carbonate.
P.5
Experiment O03 Chemical properties of ethanol
D.
Triiodomethane (iodoform) reaction
1.
In a test-tube, mix 5 drops of ethanol and 1 cm3 of iodine solution.
2.
Drop by drop, add 2 M sodium hydroxide solution until the brown colour almost disappears.
If you observe no other change, warm the tube in a beaker of hot water.
3.
Note what happens and smell the product cautiously.
E.
Reaction with sodium (Work at a fume-cupboard, with your teacher present)
1.
Pour about 1 cm3 of ethanol into a test-tube.
2.
Using forceps, pick up a 1 mm cube of sodium and remove the oil from its surface on filter
paper. Drop the sodium into the ethanol.
3.
With the front of the fume cupboard pulled down as far as is practically possible, test the
gas with a lighted splint.
4.
Pour a little of the product from step 2 on to a watch-glass, leave in the fume cupboard and
allow to evaporate. Describe what remains.
F.
Esterfication
1.
Into a test-tube, pour 2 cm3 of ethanol and 1 cm3 of glacial ethanoic acid.
2.
With care, add 2-3 drops of concentrated sulphuric acid.
3.
Warm gently for a few minutes but do not boil.
4.
Pour the product carefully into a beaker containing 10 cm3 of 1 M sodium carbonate
solution. Stir and smell. Note your observations.
P.6
Experiment O03 Chemical properties of ethanol
G. Dehydration
1.
Push enough ceramic wool down to the bottom of the test-tube to fill it to a depth of
2 cm.
2.
Using a pipette, drop 2 cm3 of ethanol onto the ceramic wool and allow to soak into the
wool.
3.
Fill up the rest of the test-tube with the pumice stone.
4.
Sep up the apparatus shown in figure 3, in the fume-cupboard, making sure clamp(A) is at
the open end of the test-tube.
Figure 3
5.
Holding the Bunsen burner in your hand, heat the pumice stone quite strongly (without
melting the tube!) and occasionally heat the ethanol gently to drive the vapour over the hot
pumice.
6.
Allow the first bubbles to escape (this is displaced air) before collecting the gas over water.
7.
Collect a tube of gas (two if possible), cork and place in a rack.
8.
Test separte tubes of gas as follows and note your observations.
(a) Shake with 1-2 drops of bromine water.
(b) Shake with 1-2 drops of acidified potassium permanganate solution.
P.7
Experiment O03 Chemical properties of ethanol
Name:
Seat No.:
Date:
Grade:
Results Table (Reactions of ethanol)
Property/Reaction
A
B
C
Observations
a.
Solubility in water
a.
b.
pH of solution.
b.
a.
Mild oxidation:
a.
Smell.
b.
Fehling's solution.
c.
Silver mirror test.
Further oxidation:
a. Smell.
b. Universal indicator paper.
c. Sodium carbonate.
D
Triiodomethane reaction
E
Reaction with sodium
F
Esterification
G
Dehydration
a. Bromine water
b.
b.
c.
a.
b.
c.
a.
b.
Acidified potassium permanganate
solution
Questions
1.
Which of the reactions of ethanol produced a reducing agent? What is the reducing agent?
2.
Which of the reactions of ethanol produced an acidic compound? The smell should give you
a clue as to what it might be. What is the acidic compound?
3.
What conditions and relative proportions of reactants are used in the oxidation of ethanol to
favour the production of (a) ethanal, (b) ethanoic acid?
P.8