Sorry for the delay on Reagent Thursday. New Note: Reagent Thursday has been cancelled and replaced with Reagent Day, which will be held off until I complete the preparation of functional groups blog posts. But here's one Reagent Day article for us to see:
For the first installment of Reagent Day, chromic acid will be the featured reagent for us to talk about today. What makes chromic acid so confusing is the number of sources it can be made from. Usually, due to safety reasons, it is often made in situ (in the flask) rather than being dispensed in a bottle. Potassium chromate, potassium dichromate, chromium trioxide, sodium dichromate, or sodium chromate mixed with acid all form this very chromic acid.
Oxidation from chromic acid oxidizes primary alcohols to carboxylic acids, secondary alcohols to ketones, and aldehydes to carboxylic acids.
How? Primary alcohol oxidation proceeds via 1,2-addition where chromic acid is the electrophile. Then a base performs an "E2" reaction, only the bond goes to the carbonyl bond. Then H3CrO4 leaves the molecule and deprotonating the carbonyl turns it into an aldehyde, further oxidized to a carboxylic acid via hydration, 1,2-addition, E2, and deprotonation.
Secondary alcohol oxidation goes via ***not shown***
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