Experiment 23. The preparation of acetanilide from aniline.
Safety Features:
- 1. Aniline is toxic and can be absorbed through the skin. Use
in a fume hood.
- 2. Concentrated hydrochloric acid can cause severe
burns.
- 3. Acetic anhydride is lachrymatory.
Procedure:
To 60 mL water in a 100 mL Erlenmeyer flask add 2.5 mL
concentrated hydrochloric acid with mixing.
The next step must be done in the fume hood.
Add 2.5 mL aniline (density 1.02 g cm-3) and swirl the mixture.
If the solution is coloured, add a small amount of decolourising
charcoal, swirl the flask for about one minute, and filter off
the carbon.
In a separate container dissolve 4 g sodium acetate
in 10 mL water.
Warm the anilinium chloride solution to 50C on a
water bath and add 3 mL acetic anhydride (density 1.08 g cm-3).
Swirl to effect dissolution and add the aqueous sodium acetate
quickly. Swirl the flask a couple of times and set it in an
ice-bath for 20 min.
Filter, with suction, the crystals of the amide formed and wash
with a small amount of ice-cold water. Continue to apply suction to the Büchner
funnel for a few minutes.
Transfer the crystals to small weighed beaker and dry them for about 15 minutes
in an oven kept at 50-55 °C.
Determine the yield and melting point of your product and submit it for assessment.
Inspect the i.r. spectra of the
aniline
(starting material) and
acetanilide
(product) and record on your worksheet the position of the band which
appears during the acetylation (see Appendix 3).
Relate this to the reaction occurring.
Carry out the nitrous acid test on the 1°
aliphatic amine and the on the 1°, 2° and 3° aromatic amines
provided. Record your results in tabular form.
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