Required Practical 5 - Oxidation of Alcohols

State the reagents used for the oxidation of a primary alcohol.

Alcohol, acidified potassium dichromate (VI) and dilute sulfuric acid

State the conditions needed for the partial oxidation of a primary alcohol.

Excess alcohol and distillation apparatus

State the observation seen when a primary alcohol is oxidised using acidified potassium dichromate (VI).

The mixture turns from orange to green

State the safety precautions that should be taken when carrying out a distillation.

Wear gloves (oxidising agent is toxic) and concentrated sulfuric acid is corrosive

Wear goggles 

Describe a method to partially oxidise propan-1-ol to pronanal.

1. Add about 10cm³ of dilute sulfuric acid to a round-bottomed flask

2. Add 3g of potassium dichromate (VI) to the acid and some anti-bumping granules

3. Shake until mixed

4. Add 1.5cm³ pronan-1-ol from a dropping pipette, shaking

5. Assemble the distillation apparatus

6. Gently heat and distil the propanal into a conical flask

Draw a diagram of the distillation apparatus. 

Why does the water need to flow through the condenser in a specific direction? 

It must enter at the bottom and leave at the top, as it allows the condenser to fill completely so that all of the vapour can condense 

Where should the bulb of the thermometer be relative to the condenser?

At the T-junction that connects the condenser

How should flammable organic reactants be heated?

In a water bath over a bunsen burner, or using an electric heater

State the conditions needed for the full oxidation of a primary alcohol. 

Excess potassium dichromate (VI) and reflux apparatus 

Describe a method for the full oxidation of a primary alcohol.

1. Measure 5cm³ water into a boiling tube and add 6g of potassium dichromate (VI)

2. Add 1.5cm³ pronan-1-ol into a round-bottomed flask and ass 5cm³ water and a few anti-bumping granules 

3. Set the apparatus for reflux

4. Add 2cm³ concentrated sulfuric acid down the condenser and then add the oxidising agent solution

5. Heat using a water bath and then distil the product off using the distillation apparatus 

How does a reflux apparatus work?

The condenser prevents organic vapours from leaving the mixture by condensing them back into the mixture

Why should the end of the tube be left open in reflux?

To allow gas to escape as pressure build-up can cause the apparatus to smash

Why are anti-bumping granules used? 

It stops the mixture from bubbling too much