During oxidation, which compound remains unreacted in the presence of acidified potassium dichromate?

In the presence of acidified potassium dichromate, a ketone remains unreacted due to its stable structure. Ketones are characterized by the carbonyl group (C=O) flanked by carbon atoms, making them less reactive towards oxidation compared to aldehydes or alcohols. Acidified potassium dichromate is a strong oxidizing agent and can oxidize primary alcohols to aldehydes and then to carboxylic acids, as well as secondary alcohols to ketones. However, ketones do not undergo oxidation to any higher oxidation state under these conditions, which is why they remain unchanged while other organic compounds react.

On the other hand, aldehydes are easily oxidized to carboxylic acids, alcohols can be oxidized to aldehydes or ketones as noted, and carboxylic acids do not typically undergo oxidation under these conditions since they are already in a fully oxidized state. Thus, the ketone's stability and lack of reactivity in this specific oxidative environment solidify its role as the unreacted compound.