Oxidation Reaction of Alcohol With Alkaline KMnO4

The aim of this experiment is to study the oxidation reaction of alcohol with alkaline KMnO₄ .

A substance undergoes oxidation when another element or compound adds oxygen atoms. These elements or compounds are known as oxidising agents.  Alcohols can be oxidised to carboxylic acid in the presence of such agents. One such reaction is:

C₂H₅OH(aq) + 2[O] → CH₃COOH (aq) + H₂O (l)

In this reaction, ethanol, a highly flammable substance,  undergoes oxidation to form ethanoic acid. Alkaline potassium permanganate acts as an oxidising agent by producing nascent oxygen. The decolourisation of potassium permanganate characterises the reaction. 

Sodium hydrogen carbonate (also known as sodium bicarbonate or baking soda), reacts with ethanoic acid, to form a brisk effervescence of carbon dioxide. This is a confirmatory test for carboxylic acid.

Apparatus and materials are required

Apparatus

• Beaker (250 mL) with distilled water
• Beaker (100 mL)  with 1% alkaline potassium permanganate
• Empty beaker – 50 mL
• Boiling tube – 1 
• Dropper – medium size
• Measuring cylinder – 10 mL
• A pair of tongs
• Funnel 
• Filter paper
• Test tube holder 
• Spatula
• A stand with ring
• Tripod stand with wire gauze

Materials:

• Ethanol
• 1% solution of alkaline potassium permanganate
• Sodium hydrogen carbonate
• Distilled water

To perform this experiment, steps to be followed in the following manner:

Procedure

• Take 3 ml of ethanol in a boiling tube and place it in a water bath. 
• To the boiling tube add two or three drops of 1% alkaline KMnO₄ solution.
•  Warm the contents till the reaction mixture decolourises.
•  Filter the solution and then add a pinch of sodium hydrogen carbonate (NaHCO₃).

In this experiment, we learnt that:

• A few drops of 1% alkaline KMnO₄ are added and the solution attains pink colour which is placed in a water bath for the oxidation to occur. 
• As KMnO₄ is consumed for the oxidation of ethanol, the pink colour disappears and it produces ethanoic acid. 
• This is confirmed by adding sodium hydrogen carbonate which produces brisk effervescence due to the evolution of CO₂ gas. 

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