Question

I'm reading Bard'sElectrochemical Methods. He cites the oxidation of p-aminophenol in acid solution. I haven't taken organic chemistry in a while and don't understand why oxidation takes place in acid. The pKa's of the amine and alcohol are 5 and 10, respectively. If you have a solution, say pH 1, wouldn't both moieties remain protonated and nothing happen?

Answer 1

In an acid solution, the oxidation of p-aminophenol occurs because the phenolic O-H group is a stronger acid compared to the alcoholic O-H group. This allows for the electron donation by oxygen and the formation of an aldehyde and an amine during the oxidation process.

Step-by-step explanation:

The oxidation of p-aminophenol in an acid solution occurs because the phenolic O-H group is a stronger acid (pKa ~10) compared to the alcoholic O-H group (pKa ~16). In a solution with a low pH, such as pH 1, both moieties would indeed remain protonated.

However, the O-H bond in the phenolic group is more easily cleaved due to the electron donation by oxygen, which allows for the formation of an aldehyde and an amine (or ammonia in the case of a primary amine) during the oxidation process.