The four alcohols ethanol, butan-1-ol, butan-2-ol and 2-methylpropan-2-ol are added to test tubes and reacted with acidified potassium permanganate. State any visible changes you would observe in each test tube and any odors that would be produced.
Acidified KMnO4 is a strong oxidizing agent, oxidizing primary alcohols to carboxylic acids and secondary alcohols to ketones. Tertiary alcohols are resisitant to oxidation under identical conditions. As KMnO4 is used up in this reaction, the purple colour of KMnO4 disappears when it participates in such reactions and persists, when it does not.
Ethanol and Butan-1-ol are primary alcohols, hence on addition of KMnO4 solution to the test tubes containing these two alcohols, the purple colour disappears immediately.
Butan-2-ol is a secondary alcohol which is oxidizable to 2-butanone upon treatment with acidified KMnO4, hence the corresponding test tube would show gradual disappearance of the pinkish purple colour of KMnO4.
2-Methylpropan-2-ol is a tertiary alcohol, resistant to oxidation with acidified KMnO4, hence the corresponding test tube would retain the pinkish purple colur of KMnO4.
In none of the test tubes, however, any recognizable smell is expected.