To a 500 mL three-neck flask were added o-xylene (16.4 mmol), paraformaldehyde (36.3 mmol), concentrated hydrochloric acid (16 mL), and ionic liquid catalyst (4.92 mmol). The reaction mixture was stirred at 70 °C for an appropriate time. After completion of the reaction, the mixture was filtered and extracted with dichloromethane (3 x 20 mL). The organic phases were combined and washed sequentially with saturated NaHCO3 solution (2 x 20 mL) and deionized water (2 x 20 mL). The organic phase was dried with anhydrous sodium sulfate, filtered and concentrated to dryness under reduced pressure. The organic residue was redissolved in dichloromethane and analyzed by HPLC. The target products, 1,2-bis(chloromethyl)-4,5-xylene and 3,4-dimethylbenzyl chloride, were separated by silica gel column chromatography and structurally characterized by 1H NMR. The remaining aqueous catalytic solution was concentrated under reduced pressure to a colorless liquid in 95% yield. The same reaction conditions were available for the next experiment.
