Question

How do you add a hydroxyl group to an alkyl chain of a carboxylic acid?

Answer 1

You can use the Hell-Volhard-Zelinski reaction to add it on the `alpha` carbon.

Recall that `"PBr"_3` can be used to substitute a hydroxyl group for a `"Br"`. The enol tautomer of this new acyl bromide can attack a `"Br"_2`, then get hydrolyzed to return to a carboxylic acid, except with an `alpha`-bromine.