Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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methyl ethyl ketone : CH3 CO CH2 CH3
acetone : CH3 CO CH3
chloroform : CHCl3
potassium hydroxide : KOH
ethanol : CH3CH2OH
Class:
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elem=C,Cl
organic
Summary:
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Acetone and chloroform react with each other in strongly alkaline
environments, building a compound, called chloretone or chlorbutol.
Formal name of the compound is 1,1,1-trichloro 2-methyl 2-propanol,
formula CCl3 C(CH3)(OH) CH3.
A similar reaction is observed, when MEK is used instead of acetone,
but the reaction is much less vigorous.
Description:
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Sequence 1:
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Dissolve some potassium hydroxide in ethanol (96%) and add a little
chloroform to the liquid: The liquid becomes turbid. A white precipitate
is formed. This precipitate probably is finely divided potassium hydroxide.
Add a fairly large amount of acetone: The liquid becomes hot (50 C ???) and
starts foaming (probably acetone and/or chloroform starts boiling). A thick
white precipitate is formed, much more than there was before addition of
the acetone.
Pour the turbid liquid and precipitate at once in a beaker, filled with
cold water: A viscous oil-like liquid is formed, which slowly sinks to
the bottom of the beaker. A thin layer of this same oil-like liquid is
floating on the water. Long needle-like crystals of a few cm are formed
as well on the water surface and on the glassware of the beaker.
A very strong camphor/mint like odour is produced. The smell has a pleasant
cooling/refreshing effect on the throat and nose. It also appears to cause
a certain dullness after some time.
Sequence 2:
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Mix 1 volume of chloroform with 5 volumes of acetone and add a solution of
potassium hydroxide in ethanol (96%) to the mixture: Formation of a white
precipitate (probably KOH) and after settling the liquid is clear and
colourless. The reaction is fairly vigorous, the liquid becomes hot and
seems to boil for a while.
Add the clear liquid to a large volume of water, without the white precipitate:
A large oil-like drop of a slightly turbid liquid is formed at the bottom.
Isolate the drop and leave in contact with air: A white crystalline solid
is formed when the more volatile components evaporate from the oil-like
drop. A very strong mint/camphor like smell is produced, with a strong
cooling/refreshing effect. The water, separated from the oil-like drop,
which is completely clear and colourless also has a strong mint-like smell.
Remark:
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The needle like crystals have structure as follows:
OH
CH3 ---- C ---- CH3
CCl3
This compound is called chloretone or chlorbutol.
The oil-like liquid consists for a large part of chlorbutol and contains
some water, acetone and chloroform. When the liquid is left in contact with
air, then the acetone and chloroform quickly evaporate and a solid is formed.
Sequence 3:
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Dissolve some solid KOH in ethanol (96%) and add a mixture of MEK and CHCl3
(in a ratio, approximately 3 volumes of MEK : 1 volume of CHCl3): When the
two clear liquids are mixed, a coarsely dividid white precipitate is formed
(this probably is solid KOH, precipitated by the MEK and chloroform). This
precipitate quickly goes to the bottom of the beaker. There is no noticeable
production of heat (this is a strong difference with the reaction, where
acetone is used).
Heat the liquid, containing the white precipitate, to appr. 60 C and shake
well: No visible changes. As soon as shaking stops, the white precipitate
quickly goes to the bottom again.
Split up the white precipitate and the colourless liquid.
Add some water to the white precipitate: The solid immediately dissolves.
This confirms the idea that this is solid KOH, precipitated from the mixture
of ethanol, MEK and chloroform.
Add the colourless liquid to a large quantity of water and shake well: After
shaking, a large drop of an oil-like liquid collects at the bottom of the
beaker. The volume of this drop is comparable to the original volume of
chloroform used. A fairly strong mint-like odour can be observed, albeit
less pungent than the odour of the acetone-product.
Remark: MEK and acetone show similar reactions, but MEK is less reactive. The
MEK-product formed is less pungent and has a softer mint-like smell. The
smell of the reaction product is pleasant and refreshing.