Oxidation of propan-1-ol to produce propanal and propanoic acid

Pictures

Procedure 1A: Making Propanal

• Carefully add 20cm3 of acidified potassium dichromate solution (K₂Cr₂O₇) to a 50cm3 pear-shaped flask, and cool it in an ice water bath.

• Set the flask up for distillation whilst in the ice-water bath

• Measure 1.5cm3 of propan-1-ol into a measuring cylinder and add 5cm3 of distilled water into this.

• Using a pipette, add the propan-1-ol solution, a few drops at a time, to flask. Wait for reaction to subside before adding more.

• When all of solution is added, remove the ice-water bath and allow flask to cool at room temperature. (approx. 5 mins)

• Light a burner under the flask and heat gently with a small flame, collect 3-4cm3 of clear, colourless liquid in a test tube immersed in cold water in a beaker.

1A

Procedure 1B: Testing for Propanal

1B

• Silver mirror test

- Prepare a sample of Tollen's reagent by adding 5 drops of sodium hydroxide solution to 2cm3 of silver nitrate solution in a test tube

- Add just enough dilute ammonia solution so that the brown precipitate dissolves completely. Gently warm the test tube in a water bath.

- Add 10 drops of distillate. If propanal present, a silver mirror will appear on the walls of the tube

• Magnesium Ribbon

- Add a small piece of magnesium ribbon to the distillate

- Propanal does not react with magnesium, so no reaction should be observed

• Sodium hydrogecarbonate

- No effervescence should be observed

• Fehling's solution

- Add 1cm3 of Fehling's solution to 1cm3 of distillate in test tube

Place test tube in beaker of hot water. A colour change to reddish-brown shows presence of propanal.

1. carefully add 20cm3 of acidified potassium dichrmoate solution to a 50cm3 pear-shaped flask. Cool the flask in an ice-water bath

2. set the flask up for reflux, keep it in the ice water bath

3. place a few anti-bumping granules into the pear-shaped flask

4. measure 1.5cm3 of propan-1-ol into a measuring cylinder, add 5cm3 of distilled water to this

5. use a pipette, add the propan-1-ol solution which you made in the previous step, add a few drops at a time, down the reflux codenser. MUST be done slowly, let the reaction to subsite before adding more

6. when all propan-1-ol is added, remove the ice-water bath, allow the pear-shaped flask to warm at room temp (estimated 5 mins).

7. light a burner under the flask, heat gently under reflux, use a small flame for 30 mins

8. distill the product, use distillation apparatus. Collect 3-4cm3 of clear, colourless liquid in a test tube, immersed in a beaker with cold water. Distillate MUST be specified amount due to several tests that are done with it.

Process

Hazards:

• Propanal and Propan-1-ol are both flammable
• Propanal is an irritant
• Burners can cause skin burns
• Potassium dicromate can be corrosive/irritant
• The type of thermometer used
• Ice water bath; spillage
• Silver nitrate is corrosive and toxic
• Ammonia solution may be corrosive to metals and can cause severe skin burns and eye damage
• Fehling's solution can cause serious eye damage
• Tollen's reagent is toxic and corrosive
• Sodium hydroxide is dangerous to ingest
• Glass equipment can break
• Silver nitrate is sensitive to light

Hazards

Tollen's reagent is used during the silver mirror test.

there should be no reaction between the distillate and the magnesium ribbon. Which means nothing should be seen happening in the test tube.

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heating under reflux and distillation

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No effervesence is caused.

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heating a chemical reaction for a certain amount of time, whilst simaltaneously cooling the vapour produced into it's liquid form, using a condenser

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