Describe how you would differentiate a sample of butanal and butan-2-one.

You would add tollen's reagent to both samples. The butanal would form a silver mirror, whereas, butan-2-one would remain unchanged. This is due to the fact that an aldehyde can be oxidised to a carboxylic acid and an reduce the oxidising reagent to solid silver (mirror) and ammonia. However, ketones cannot be oxidised so the reagent cannot be reduced.