Synthesis of p-Methoxyphenylacetone
by Psycho Chemist

In a 1000 mL flask with double surface condenser/drierite tube, reflux 600 mL acetic anhydride, 100 mL pyridine (dry) and 100 g 4-methoxyphenylacetic acid for 18 hrs with good stirring. Thereafter, distill off 600 mL acetic acid, acetic anhydride and pyridine over a 30x500 mm helices packed column. The residue is added - when cooled down (!) - to 500 mL water, and stirred for 30 min. to hydrolyze any present acetic anhydride. The mixture is then extracted with 5x200 mL methyl tert-butyl ether, and the pooled extracts are washed with 4x100 mL 20% sodium hydroxide (keep the alkaline washings), and 200 mL saturated aqueous NaCl. The organic layer is dried over sodium sulfate, evaporated (rotary evaporator, recover the solvent), and the residue distilled to give 60 g p-methoxyphenylacetone, bp 145-165°C at about 20 mm Hg. Recovery of unreacted 4-methoxyphenylacetic acid: The alkaline washings are pooled, acidified (pH 1) with hydrochloric acid, and extracted with 4x100 mL methyl tert-butyl ether. The pooled organic extracts are evaporated (rotary evaporator, recover solvent), and the residue is mixed with 100 mL toluene or benzene. The solution is refluxed with a Dean-Stark adapter/double surface condenser, to remove any present water, then the solvent is distilled off in vacuum to get 25g of unreacted p-methoxyphenylacetic acid.