Organic Chemistry, "Change" - Part 21, Oxidation of an Alcohol Using Sodium Dichromate in Sulfuric Acid Solution

 Greetings,

This post covers oxidation of an alcohol using chromic acid.  Chromic acid has traditionally been used because it is a strong oxidizing agent and is readily available. A drawback is that chemical wastes containing chromium are expensive to dispose of because of the toxicity of the metal.

The reaction scheme of a 2-degree alcohol oxidation (to form a ketone) via chromic acid is presented below. Chromic acid is formed in situ during oxidation of an alcohol by the addition of sodium dichromate and sulfuric acid. Sodium dichromate is used because it is much more stable (and safe) to use than chromic acid. Sodium dichromate is shelf-stable and easily utilized because it exists as a crystalline solid.

The reaction mechanism involves the formation of an intermediate alcohol-chromate ester via addition reaction. A rapid electron rearrangement then proceeds with the release of the chromium portion of the intermediate and the oxidized alcohol product (a ketone). Oxidation is indicated from the loss of a hydrogen atom (from the alcohol) during the reaction. Further evidence of oxidation comes from reduction of the chromium atom from an oxidation state of VI to IV.

That's all for this post. As always, thank you for reading!