Oxidising agents

The idea

Substances capable of adding oxygen to others are oxidising agents; alkaline potassium permanganate or acidified potassium dichromate oxidise alcohols to carboxylic acids.

From alcohol to acid

Ethanol is an alcohol. Ethanoic acid is a carboxylic acid.

What kind of substance can turn an alcohol into a carboxylic acid?

• One that adds oxygen
• One that removes water
• One that adds hydrogen

Adding oxygen

Press Next step.

Oxidising agents add oxygen

The agent adds oxygen to the alcohol, so the alcohol is oxidised to a carboxylic acid.

Substances capable of adding oxygen to others are oxidising agents. Alkaline potassium permanganate or acidified potassium dichromate oxidise alcohols to carboxylic acids.

Notes

Substances that add oxygen to others are oxidising agents. Alkaline potassium permanganate or acidified potassium dichromate oxidise alcohols to carboxylic acids.

Check yourself

What are substances that add oxygen to others called?

Which pair oxidises alcohols to carboxylic acids?

What does oxidising an alcohol give?

How many oxygen atoms does the ethanoic acid molecule in the picture have?

Answer: 2

Ethanoic acid, CH₃COOH, has 2 oxygen atoms, one more than ethanol.

• Dehydrating agents. A dehydrating agent removes water, as concentrated sulphuric acid does to ethanol.
• Catalysts. Catalysts cause a reaction to occur or proceed at a different rate. Substances that add oxygen are oxidising agents.
• Oxidising agents — correct. Yes!
• Alkaline potassium permanganate or acidified potassium dichromate — correct. Yes!
• Sodium metal. Sodium reacts with alcohols to evolve hydrogen. It does not turn them into carboxylic acids.
• Nickel or palladium. Nickel and palladium are catalysts for adding hydrogen to unsaturated hydrocarbons.
• An alkene. Ethanol is turned into ethene by dehydration with hot concentrated sulphuric acid, not by an oxidising agent.
• A carboxylic acid — correct. Yes!
• An ester. An ester forms when an acid reacts with an alcohol.