At several points in the synthesis of para-Aminobenzoic Acid (PABA), having the correct acidity/basicity of the solution is critical in obtaining a good yield of product. In answering each of the following questions, include chemical reactions illustrating the importance of hacing the correct pH at that point in the reaction sequence.

a. In the first step of the synthesis of PABA, why was concentrated hydrochloric acid added to the mixture of water and p-toluidine?

b. In the first step of the synthesis of PABA, why was it necessary to add sodium acetate to have reaction of p-toluidine with acetic anhydride?

c. In the second step of the synthesis of PABA (i.e., oxidation of the methyl group with potassium permanganate), why was magnesium sulfate added to the reaction mixture?