Methods of producing terephthalic acid are described. The methods involve using a p-xylene stream enriched with p-toluic acid and optionally terephthalic acid at impurity levels. The p-xylene stream enriched with p-toluic acid, a solvent comprising an ionic liquid and optionally a carboxylic acid, a bromine source, a catalyst, and an oxidizing agent are contacted to produce a product comprising terephthalic acid.