Hydrochloric Acid → 3-Acetoxy-2-methylbenzoic acid

Participants

Reaction Conditions

Reaction Steps

A solution of 3-benzyloxy-2-methylbenzoic acid (50 g, 0.21 mol) and sodium hydroxide (20 g, 0.5 mol) in 700 g of water and 2 g of 5% Pd/C catalyst (50% water-moist) is added to a 21 steel autoclave with an aerating stirrer. 10 bar of hydrogen are injected at a temperature of 25° C. and a stirring speed of 800 rpm. Consumed hydrogen is replaced by repeated injection. After 15 min, the absorption of hydrogen falls off. The catalyst is filtered off at room temperature through a pressure filter. 735.8 g of a crude solution are obtained, from which 7.1g of toluene are separated off in a separating funnel. The aqueous crude solution is cooled to 0° C. in a 1 l four-necked flask with a pH meter. The pH is 14. 31.3 g (0.3 mol) of acetic anhydride are added dropwise in the course of 5 min; the pH falls to 6.0. The solution is then slowly treated (pH 1.1) with 49.3 g (0.5 mol) of hydrochloric acid (37% strength). A white precipitate is deposited in the course of this. The suspension is stirred for a further half hour, then the precipitate is filtered off and washed twice with 50 g of ice water. After drying, 37.5 g (93.7% of theory) of 3-acetoxy-2-methylbenzoic acid are obtained (melting point: 147° C.).

Provenance & Evidence