Final answer:
Ketones generally do not react with Fehling's solution and the solution remains colorless. However, α-hydroxy ketones can show a positive reaction due to their ability to isomerize into an aldehyde.
This differs from aldehydes, which are easily oxidized by Fehling's solution, resulting in a red precipitate of copper(I) oxide.
Step-by-step explanation:
When a ketone is added to Fehling's solution, there is typically no reaction because ketones do not have the necessary functional group to be oxidized by Fehling's solution. Fehling's solution is used to test for the presence of aldehydes, which are easily oxidized.
Therefore, the solution typically remains colorless when a ketone is added. However, if the ketone is an α-hydroxy ketone, it can react with Fehling's solution because the ketone can be isomerized into an aldehyde under the basic conditions of the test. But for ordinary ketones, no reaction is observed.
On the other hand, aldehydes react with Fehling's solution because of the presence of the aldehyde functional group, which can be further oxidized. This oxidation of aldehydes results in a red precipitate of copper(I) oxide (Cu2O), indicating a positive result for the presence of aldehydes.