Patent ID: 8664424

Claim:
A method for preparing 2,5-dimethylphenylacetic acid, comprising: (1) producing 2,5-dimethylbenzyl chloride by performing a chloromethylation reaction comprising the following steps: mixing together p-xylene, a solvent ionic liquid, paraformaldehyde, and concentrated hydrochloric acid to obtain a first reaction mixture, wherein the mole ratio of the p-xylene, paraformaldehyde, and ionic liquid is 1:1.1-5:0.01-1; heating the first reaction mixture to a predetermined temperature; contacting the first reaction mixture with hydrogen chloride gas and allowing the chloromethylation reaction to proceed; maintaining the temperature of the reaction mixture at the predetermined temperature until 30 minutes after the reaction is completed; cooling the chloromethylation reaction solution, and allowing the reaction solution to layer into an organic layer and a water layer; and rectifying the organic layer under vacuum to obtain 2,5-dimethylbenzyl chloride; and (2) subjecting 2,5-dimethylbenzyl chloride to carbonylation and hydrolyzation reactions, comprising the following steps: adding to a reactor the 2,5-dimethylbenzyl chloride obtained from the chloromethylation reaction, an acid binding agent, and a catalyst to obtain a second reaction mixture; heating the second reaction mixture to a predetermined temperature; contacting the second reaction mixture with carbon monoxide gas and allowing the carbonylation and hydrolvzation reactions to proceed; after the reactions are completed, cooling the carbonylation and hydrolyzation reaction solution; and then adding liquid caustic soda to the cooled solution under a nitrogen atmosphere, and stirring; allowing the reaction solution to layer into an organic layer and a water layer; adjusting the pH of the water layer to a pH of 1; and then filtering the reaction solution to obtain 2,5-dimethylphenylacetic acid.