New Process for Synthesis of p-tert-Butyl Benzoic Acid Methyl Ester using Methanesulfonic Acid as Catalyst

p-tert-Butyl benzoic acid methyl ester was synthesized from p-tert-butyl benzoic acid and methanol using methanesulfonic acid as catalyst by two different production processes A and B. Process A used the one-step method, the yield 85.8% was obtained when the molar ratio of acid to alcohol is 1∶7, 10% catalyst (molar percent of acid), and refluxed for 8 h. Under the same condition, the reaction was performed using process B, which was separated for two stages. In the first stage, the molar ratio of acid to methanol is 1∶3.5, methanol and the produced water were separated by distillation after refluxed for 3 h. Then the same amount of methanol as the first stage was added, the reaction refluxed for further 5 h, the yield of product was up to 95.3%. The product was characterized by IR and index of refraction.