Aromatic electrophillic substitutionAromatic electrophillic substitution
SyntheticPage 569
Published Aug 09, 2012
In a 2 Lt four necked round bottom flask (assembly was set up in cooling tub) equipped with a mechanical stirrer, 500 mL dropping funnel, thermometer, calcium chloride guard tube, was charged benzene (550 mL). This slurry was cooled to about 5 oC and added anhydrous aluminium chloride (543 g, 4.06 mol ). Methacrylic acid (100 g, 1.31 mol) was slowly added keeping the reaction temperature below 8oC over a period of 1 h. Cooling removed and allowed to come to room temperature over a period of 2-3h. The reaction mixture thus obtained was heated to 50-50 oC and maintained at this temperature for 2 h. Further the reaction mixture was cooled and added to ice concentrated HCl ( ~500 g + 500 mL). The Product gets extracted in benzene. Benzene layer thus obtained was washed with water ( 250 mL) and then extracted with 15% sodium hydroxide solution (400 mL). This extraction brings the product to water layer. Aqueous alkaline solution was acidified to pH-2 with concentrated hydrochloric acid. The white crystals thus separated was washed with water (~250 mL) and dried at 70-75 oC for 8 h to get 2,2-dimethyl phenyl acetic acid as almost white crystalline solid (115 g, 53.5% based on methacrylic acid ).