Hydrochloric Acid → 3-Acetoxy-2-methylbenzoic acid

Participants

Reaction Conditions

Reaction Steps

In a flat-flanged vessel, 80.0 g of 3-hydroxy-2-methylbenzoic acid (purity 97.78%) are dissolved in 320.0 g of water and 120.0 g of sodium hydroxide solution (w=30%), which results in a pH of 6.9. The clear solution is cooled to 0° C. and adjusted to pH=9 by metering in sodium hydroxide solution (w=30%). Acetic anhydride and sodium hydroxide solution are now simultaneously metered in at 0-5° C. in such a way that the pH remains within the range of 8.8-9.2. 112.6 g of acetic anhydride and 172.25 g of sodium hydroxide solution (w=30%) are metered in within 2.5 h. Afterwards, the mixture is stirred for a further 1.5 h. A second flat-flanged vessel is charged with 150.0 g of water and cooled to 0° C. The reaction mixture of the first vessel and hydrochloric acid (w=37%) are simultaneously metered in at a maximum of 5° C. in such a way that a pH of 3.8-4.2 is maintained. The product precipitates out as a white precipitate. The pH is adjusted to 1 by metering in hydrochloric acid (w=37%). The product is filtered off with suction and washed with 500.0 g of water. The precipitate is dried in a vacuum drying cabinet at 60° C. for 16 h. 172.6 g of 3-acetoxy-2-methylbenzoic acid (purity 99.9%) are obtained. This corresponds to 99.28% of theory.

Provenance & Evidence