Preparation of propanone from propan-2-ol

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                          Date:   11/10/2011

Exp. No.:            23

Title:                Preparation of propanone from propan-2-ol

Aim:        The aim of this experiment is to prepare propanone by oxidizing propan-2-ol with acidified potassium dichromate solution.

Introduction:  Ketones and aldehydes are important series in preparation of other compounds and they are commonly prepared by oxidizing alcohol which is done in this experiment.

             The experiment is an oxidation reaction where a secondary alcohol (propan-2-ol) is oxidized by acidified potassium dichromate. The reaction does not need to be heated but should be placed in an iced water bath as the reaction is highly exothermic.

The product is propanone and no catalyst is needed for the reaction.

The propanone is serparated from the reaction mixture by simple distillation and is purified using anhydrous cacium chloride.

The equation of this reaction is as follow:

Chromic acid is produced in situ by adding potassium dichromate (VI) with sulphuric acid and water.

K2Cr2O7 + H2O + 2H2SO4  2 H2CrO4 + 2 NaHSO4

The term chromic acid is usually used for a mixture made by adding concentrated  to a , which may contain a variety of compounds, including solid . Chromic acid features chromium in an  of +6. It is a strong and corrosive .

Apparatus and chemicals:

Apparatus:   Quick-fit distillation setup, anti-bumping granules, thermometer, conical flasks, beakers, filter funnel, filter paper, iced water bath, 10cm3 measuring cylinder, triple beam balance, dropper, suction flask

Chemicals:   About 3 cm3 propan-2-ol, 3 cm3 concentrated sulphuric acid, deionized water, 4g potassium dichromate (VI), 2-4-dinitrophenylhydrazine (2,4-DNP), anhydrous calcium chloride


Part 1: Oxidation of propan-2-ol and distillation

  1. About 4g of potassium dichrome solid and 10 cm3 deionized water were added to a conical flask and the flask was well shaken to allow the solid to dissolve.
  2. An iced water bath was prepared by adding some ice cubes to a beaker with tap water.
  3. 3 cm3 of propan-2-ol was added into a clean pear shape flask and the flask was placed into the iced water bath.
  4. The prepared acidified dichromate solution was added to the pear-shaped flask slowly and in small portion using a dropper.
  5. The flask was swirled during the addition of acidified potassium dichromate.
  6. After 2-3 minutes, 10 cm3 of deionized water was added to the mixture.
  7. Some anti-bumping granules were added into the pear-shaped flask.
  8. The quick-fit distillation set up was fixed and was connected with the pear-shaped flask.
  9. The distillate at around 58oC was collected with a boiling tube.
  10. Anhydrous calcium chloride was added to the product and was shaken gently.
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The Setup:

Part 2: Testing the presence of carbonyl group in the compound

  1. 2cm3 of 2,4-dinitrophenylhydrazine was added into a test tube.
  2. 3 drops of the product were added into the test tube.
  3. The crystals were collected by using a suction flask.

The setup:


  1. Propan-2-ol had a smell of disinfectants.
  2. Propan-2-ol, sulphuric acid, the organic products were all colourless.
  3. 2,4-dinitrophenylhydrazine solution was yellow in colour.
  4. The sulphuric acid had an irritating smell.
  5. The anhydrous calcium chloride was in white ...

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This is a highly detailed, well laid out experiment with excellent alternative methods. This piece of work is 5*