Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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ethanol : CH3CH2OH
sodium hydroxide : NaOH
dichloromethane : CH2Cl2
ammonia : NH3
acetone : CH3 CO CH3
iodine : I2
potassium iodide : KI
Class:
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elem=C,I
organic
Summary:
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This experiment is performed in order to determine, whether iodoform (CHI3)
shows a reaction, similar to chloroform, when treated with acetone in a
strongly alkaline environment. The result of this experiments suggests
that indeed a similar reaction occurs, resulting in the formation of a
compound with a sweetish mint-like odour.
Description:
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The first step is the formation of iodoform. If this chemical is available
already, then it can be used directly.
Formation of iodoform:
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Dissolve some iodine in a concentrated solution of potassium iodide and add
some acetone and ammonia: At first glance, the liquid becomes gray (formation
of NI3.NH3 or similar components?) but after a while, the liquid becomes
yellow and a yellow precipitate is formed. This yellow precipitate is
iodoform.
Add some dichloromethane and shake well: All iodoform is extracted from the
water and the solid particles dissolve. The layer of dichloromethane becomes
yellow.
Separate the layer of dichloromethane and let the dichloromethane evaporate:
Formation of many little yellow crystals.
Reaction with acetone:
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Add the crystals to a small amount of acetone: They dissolve exceptionally
well, the liquid becomes intense yellow.
Dissolve a small amount of sodium hydroxide in ethanol (96% by weight) and
add this solution to the yellow acetone-liquid: The intense yellow colour
fades away in a few seconds and the resulting liquid is almost colourless.
It is slightly turbid, probably due to precipitation of a small quantity
of sodium hydroxide.
Add a large amount of water: All of the material dissolves, the liquid
becomes clear. The liquid appears to be a little more viscous than plain
water and hardly visible flakes are floating through the liquid. When the
liquid is shaken, then one can see that the flakes keep small bubbles of
air trapped.
Pour out the liquid over a large surface: Smell of ethanol, but besides that
there also is a clearly observable sweet mint-like odour.
OH
Does this experiment result in the formation of CH3---C---CH3 ?
CI3