3-Chloro-2-methylbenzoic acid

118-90-1

7499-08-3

7499-06-1

133232-56-1

54811-38-0

In a 100 mL three-necked flask equipped with a reflux condenser, 1.36 g (10 mmol) of 2-methylbenzoic acid was suspended in 25 mL of 30% (w/w) sulfuric acid. Subsequently, 2.4 g (15 mmol) of iodine monochloride was dissolved in 5 g of acetic acid and added slowly and dropwise to the reaction mixture over 40 min. The reaction was continued at 90°C for 5 hours. Upon completion of the reaction, the mixture was poured into 90 mL of water, the precipitate was collected by filtration and washed with aqueous sodium sulfite to give 1.6 g of crystalline solid product. Analysis of the product showed the following compositional distribution: 33% 2-methylbenzoic acid, 13% 5-chloro-2-methylbenzoic acid, 9% 3-chloro-2-methylbenzoic acid, 38% 5-iodo-2-methylbenzoic acid, 5% 3-iodo-2-methylbenzoic acid, and 2% other impurities. Attempts were made to purify the above mixture by recrystallization from acetic acid or isopropanol to isolate 5-iodo-2-methylbenzoic acid, but the purity of the mixture was not significantly improved, making it difficult to obtain pure 5-iodo-2-methylbenzoic acid.