Can you mildly oxidize a ketone

The C-O double bond is formed when a base removes the proton on the carbon adjacent to the oxygen. It is also possible for pyridine to be used as the base here, although only very low concentrations of the deprotonated form will be present under these acidic conditions.

What oxidant could be used? Show the products of the oxidation of 1-propanol and 2-propanol with chromic acid in aqueous solution. Since this is a primary alcohol, there are some precautions necessary to avoid formation of the carboxyllic acid. Milder oxidants such as the Dess-Martin periodinane, and also PCC there is no water to form the carboxyllic acid would work.

Steven Farmer Sonoma State University. Jim Clark Chemguide. James Ashenhurst MasterOrganicChemistry. Objectives After completing this section, you should be able to write an equation to represent the oxidation of an alcohol. Study Notes The reading mentions that pyridinium chlorochromate PCC is a milder version of chromic acid that is suitable for converting a primary alcohol into an aldehyde without oxidizing it all the way to a carboxylic acid. Oxidizing the different types of alcohols The oxidizing agent used in these reactions is normally a solution of sodium or potassium dichromate VI acidified with dilute sulfuric acid.

Primary alcohols Primary alcohols can be oxidized to either aldehydes or carboxylic acids depending on the reaction conditions. Full oxidation to carboxylic acids You need to use an excess of the oxidizing agent and make sure that the aldehyde formed as the half-way product stays in the mixture. Secondary alcohols Secondary alcohols are oxidized to ketones - and that's it. Using the simple version of the equation and showing the relationship between the structures: If you look back at the second stage of the primary alcohol reaction, you will see that an oxygen "slotted in" between the carbon and the hydrogen in the aldehyde group to produce the carboxylic acid.

Tertiary alcohols Tertiary alcohols are not oxidized by acidified sodium or potassium dichromate VI solution - there is no reaction whatsoever. If you add one equivalent of PCC to either of these alcohols, you obtain the oxidized version. The byproducts featured in grey are Cr IV as well as pyridinium hydrochloride. Reagents for oxidation of alcohols was one of those things that made me feel really dumb when I learned organic chemistry.

It was only later that I understood that oxidation is not nearly as complicated as these weird reagents make it seem. Not only will oxidation reactions then become less mysterious. Click to Flip Click to Flip. Your email address will not be published.

Save my name, email, and website in this browser for the next time I comment. Notify me via e-mail if anyone answers my comment. This site uses Akismet to reduce spam. Learn how your comment data is processed. Next Demystifying Alcohol Oxidations. Advanced References and Further Reading 1.

To carry out the test, you add a few drops of the aldehyde or ketone to the freshly prepared reagent, and warm gently in a hot water bath for a few minutes. Figure 1: Tollens' test for aldehyde: left side positive silver mirror , right side negative. Image used with permission from Wikipedia. Aldehydes reduce the diamminesilver I ion to metallic silver. Because the solution is alkaline, the aldehyde itself is oxidized to a salt of the corresponding carboxylic acid.

The electron-half-equation for the reduction of of the diamminesilver I ions to silver is:. Combining that with the half-equation for the oxidation of an aldehyde under alkaline conditions:. Fehling's solution and Benedict's solution are variants of essentially the same thing. Both contain complexed copper II ions in an alkaline solution. Both solutions are used in the same way. A few drops of the aldehyde or ketone are added to the reagent, and the mixture is warmed gently in a hot water bath for a few minutes.

Figure 2 : Fehling's test. Left side negative, right side positive. Aldehydes reduce the complexed copper II ion to copper I oxide. The equations for these reactions are always simplified to avoid having to write in the formulae for the tartrate or citrate ions in the copper complexes. The electron-half-equations for both Fehling's solution and Benedict's solution can be written as:.

Jim Clark Chemguide. Why do aldehydes and ketones behave differently? What is formed when aldehydes are oxidized?