Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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acetic acid : CH3COOH
sulfuryl chloride : O2SCl2
acetic anhydride : (CH3CO)2O
sulphuric acid : H2SO4
Class:
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elem=C,S,Cl
acid/base
Summary:
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The combination of acetyl and sulfate, either directly, or derived from other
compounds reacts extremely energetically with water. It is remarkable that it
is this specific combination of three entities which gives extremely violent
reactions. This effect is demonstrated with different chemicals in different
combinations.
Description:
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Experiment 1: Acetic anhydride and sulphuric acid
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Take 1 ml of acetic anhydride and add a few drops of 98% sulphuric acid
(CAREFUL!! TEST TUBE MUST BE POINTED AWAY FROM PERSONS): A very violent
reaction occurs. There is a loud crackling noise and the liquid becomes very
hot.
Add more drops of sulphuric acid: Each drop leads to a violent reaction, but
from a certain point, the reaction is not that violent anymore. After adding
approximately 0.5 ml of sulphuric acid to 1 ml of acetic anhydride, the liquid
becomes quite viscous, like cold glycerol.
Experiment 2: Acetic anhydride and sulfuryl chloride
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Take 0.5 ml of acetic anhydride and add 0.5 ml of sulfuryl chloride: Both
liquids mix, the resulting liquid is pale green, no visble reaction seems to
occur. No heat is produced.
Carefully heat the liquid: The pale green color fades. On cooling down it
reappears again. No other reaction seems to occur.
Let the liquid cool down and then add a few drops of water (CAREFUL!! TEST TUBE
MUST BE POINTED AWAY FROM PERSONS): A really violent reaction occurs. There is
a loud crackling noise and when the drops of water are added too fast, then the
liquid explodes and all of it erupts from the test tube! This reaction is
extremely violent! In the reaction, quite some HCl is formed.
Experiment 3: Acetic acid and sulfuryl chloride
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Take 0.5 ml of glacial acetic acid and add 0.5 ml of sulfuryl chloride: Both
liquids mix, the resulting liquid is colorless, no other visble reaction seems
to occur. No heat is produced.
Add a few drops of water (CAREFUL!! TEST TUBE MUST BE POINTED AWAY FROM
PERSONS): A violent reaction occurs. The liquid starts boiling and when the
drops of water are added too fast, then the liquid erupts from the test tube!
This reaction is extremely violent! In the reaction, quite some HCl is formed.
Concluding remarks:
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Acetic anhydride only slowly reacts with water. It takes hours to dissolve some
of this liquid in water. The resulting liquid is acetic acid.
Sulfuryl chloride also reacts slowly with water. It takes tens of minutes or
even hours when it is added to cold water. A blob of liquid sits at the bottom
under the water and this slowly dissolves.
Acetic acid simply mixes with water, nothing else.
Sulphuric acid reacts with water, giving quite some heat, but this reaction by
far is not as violent as the reactions, described above.
The combination of acetyl and sulfate and water leads to extremely violent
reactions.
In experiment 1, acetic anhydride reacts with sulphuric acid, giving acetyl
sulfate. Apparently this reaction is extremely violent.
In experiment 2, acetic anhydride and sulfuryl chloride cannot react, but when
water is added, then sulphuric acid is formed, which can react with the acetic
anhydride.
In experiment 3, acetic acid and sulfuryl chloride cannot react, but when water
is added, sulphuric acid is formed, which can react with the acetic acid (which
possibly partially is converted to acetic anhydride and/or acetyl chloride).
A really good explanation of the observations is not given above, more
experiments and research are needed to understand all different observations.