Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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acetone : CH3 CO CH3
ethanol : CH3CH2OH
sodium hydroxide : NaOH
potassium hydroxide : KOH
trichloroethene : CHCl CCl2
Class:
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elem=C,Cl
organic
Summary:
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Trichloro ethene reacts with acetone, forming a brown substance, but only
when in a strongly alkaline environment. The exact conditions, under which
this brown substance is formed must be further investigated.
Description:
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Sequence 1:
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Dissolve some potassium hydroxide in ethanol (96% by weight) and add a mixture
of trichloro ethene and acetone: The liquid becomes turbid, a white precipitate
is formed (probably this is KOH, precipitated by the acetone and tri). After
some time, the liquid has become yellow, after one day, the liquid is brown.
Sequence 2:
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Dissolve a little amount of potassium hydroxide in ethanol (96%) and add
a mixture of trichloro ethene and aceton (1 volume of tri : 5 volumes of
acetone): The resulting liquid remains clear, no white precipitate is formed.
The liquid does not turn yellow after some time.
Add some solid sodium hydroxide: The pearls of the solid are covered by a
brown substance within a few minutes. When the liquid is shaken it turns
yellow now. After one day it is brown, just as in sequence 1.
Remark: Apparently, the brown substance is only formed when a high
concentration of hydroxide is available (near the surface of solid particles
of sodium or potassium hydroxide).
When the same sequences are performed without acetone, then no visible
reaction occurs. Apparently the ethanol does not participate in the reaction.
The smell of the liquid, containing the brown substance, differs from the
initial smell of the ethanol/acetone/tri mixture.