SDN Members don't see this ad. (About Ads) From Datqvault explanation: The carboxylic acid has the most oxidized state for carbon. The oxidation number for a carboxylic acid is +3, for an aldehyde, ether, or alcohol is +1, and for a ketone is +2. Esters have the same oxidation states as carboxylic acids. How do you calculate or assume that?