Final answer:
Secondary alcohols oxidize to ketones, while primary alcohols oxidize to aldehydes, which can further oxidize to carboxylic acids. Quinones are used instead of acetone in Oppenauer Oxidation of primary alcohols to prevent this over-oxidation, halting the reaction at the aldehyde stage.
Step-by-step explanation:
The process of oxidation of alcohols can lead to different products depending on the type of alcohol and the oxidizing agent used. Generally, when a secondary alcohol is oxidized, the outcome is a ketone. For example, the oxidation of 2-propanol (isopropyl alcohol) using an oxidizing agent such as potassium dichromate (K₂Cr₂O₇) results in the formation of propanone (acetone).
In the case of primary alcohols like ethanol, the desired product is often an aldehyde (in this case, acetaldehyde).\ However, aldehydes are more easily oxidized to carboxylic acids than alcohols are to aldehydes. Thus, a milder oxidizing agent needs to be used to halt the reaction at the aldehyde stage. In the context of Oppenauer Oxidation, where acetone is typically used with Aluminium Tertiary Butoxide to oxidize secondary alcohols, a different approach is required for primary alcohols to prevent over-oxidation.
Quinones are utilized in some selective oxidation reactions to produce aldehydes from primary alcohols without further oxidation to carboxylic acids. The mechanism involves mild oxidation conditions that are specific enough to avoid the over-oxidation that can occur if more potent oxidizing agents were used. This selective action of quinones maintains the delicate balance required to achieve the desired oxidation state, producing an aldehyde instead of a carboxylic acid.