The oxidation product of primary alcohols using PCC vs Jones oxidation is different; what is produced by PCC?

• A. Carboxylic acids
• B. Aldehydes
• C. Ketones
• D. Alcohols

Answer: (B)

PCC provides selective oxidation of primary alcohols to aldehydes. It’s a milder oxidizing system and is used under dry, non-aqueous conditions, so the alcohol is converted to the aldehyde and stops there because there isn’t enough water and the oxidant isn’t aggressive enough to push the aldehyde to the carboxylic acid. In other words, the carbon bearing the original OH becomes a carbonyl with one hydrogen attached—the aldehyde.

In contrast, Jones oxidation uses a stronger oxidant in aqueous acidic medium, which readily pushes the aldehyde further to the carboxylic acid. So the oxidation product from PCC is an aldehyde, whereas Jones would give a carboxylic acid for a primary alcohol.

For example, ethanol treated with PCC gives acetaldehyde, not acetic acid.