Why should the mixture of anhydride and anhydrous toluene be added to the mixture of aluminum trichloride and anhydrous toluene when preparing p-methyl acetophenone?

This is a typical Fourier reaction. The principle is that under the catalysis of aluminum trichloride, acetic anhydride electrophilic substitution occurs on the benzene ring of toluene. Firstly, toluene and aluminum trichloride are mixed as reactants and catalyst system. Then the anhydride was dissolved in toluene and added dropwise. Because the reaction is exothermic, the reaction speed and process are controlled by dropwise addition.