Students Discover Organic Chemistry: A Phenomena-Oriented and Inquiry-Based Network Concept (PIN-Concept) - Essentials of Chemical Education - page 284

2. Syntheses

2.1 Esterification

With the purified product (ca. 15 ml), only the Rojahn test is positive. Additionally,
the iodoform test should be made. It is positive as it should be for ethyl acetate, but
only a slight turbidity is observable.

- Note : In the same way, propyl propionate can be synthesized from propanol and
propanoic acid. This time, the iodoform test is negative as it should be. The yield
is ca. 20 ml.
- Procedure : In an Erlenmeyer flask (100 ml), 20 ml ethanol, 20 ml ethanoic acid,
and 5 ml sulfuric acid (conc.) are mixed. Shake the mixture well. It warms up
spontaneously. Let it stand for 5 min and pour it then into another Erlenmeyer
flask (100 ml) containing 75 ml water. Immediately, an organic phase separates
in the neck of the flask. It smells like an ester.
Test the crude product by means of analytical tests (Rojahn test, cerium nitrate
test, BTB test, iron chloride test).
In order to purify the crude product, transfer it with a pipe into a flask (100 ml),
add the double volume of sodium carbonate solution ( c

1 mol/l) and shake the
unstoppered flask well, until the gas evolution (CO 2 ) is finished. Then stopper
the flask and shake well. Let the phases separate.
Investigate the upper phase (purified product) with the tests.
- Result : With the crude product, the four tests are all positive. From this it can be
concluded that an ester has been produced which is still contaminated with
alcohol and acids.

¼

2.2 Ester Hydrolysis

- Procedure : In a flask (250 ml), put 60 ml sodium hydroxide solution ( c 3 mol/l)

and 15 ml ethyl acetate. Stopper the flask and shake it vigorously for 2 min. Then
pour the reaction mixture by means of a funnel into a distillation apparatus
(Fig. 9.3 ) and distil with a boiling water bath for 15 min. (Cover the upper part
of the apparatus with an aluminum foil.) Investigate both the distillate and the
residue with the analytical tests. Note that the residue must be acidified with
sulfuric acid ( c

¼

1.5 mol/l) before making the tests. (Mix 5 ml residue with
4.5 ml sulfuric acid.)
- Result : Ethyl acetate is hydrolyzed in alkaline solution into ethanol (distillate)
and acetate (residue). In the distillate, only the cerium nitrate test, the iodoform
test, and the dichromate test are positive. This is the pattern of ethanol.
In the residue, the iron chloride test is positive (lower phase orange) indicating
the presence of ethanoic acid (or acetate). The BTB test is also positive, but it is
not conclusive for carboxylic acids because the residue was acidified with
sulfuric acid.

¼