Why does only the amino group react in the synthesis of paracetamol?

[jsmith613]

I was reading through my textbook and apparently when 4-aminophenol reacts with an acyl chlordie / acid anhydride (as in the synthesis of paracetamol) only the R-NH₂ group reacts and NOT the R-OH group.

Why is this?

 

[MrSid]

The amino group is considered more nucleophilic to attacking the acyl group and displacing chloride, than a phenolic hydroxyl. The phenolate anion will not be present in enough quantity to interefere (it is somewhat better nucleophile than free phenol hydroxyl).

Of the phenolate ester that is formed under strongly basic conditions, it is also a good electrophilic species like the acyl chloride, and is amidated by the amino group attack on the ester carbonyl releasing the phenolate anion. One wouldn't expect to see much if any ester as a result.