2-Amino-5-methylbenzenesulfonic acid → 2-Amino-5-methylphenol

Participants

Reaction Steps

The Na salt of 2-amino-5-methyl-benzenesulphonic acid is reacted with 80% by weight of KOH to give the K salt of 2-amino-5-methyl-phenol (300° C.; 15 to 20 bar; 3h), the molar ratio of KOH to 2-amino-5-methyl-benzenesulphonic acid preferably being from 10:1 to 15:1. The reaction mixture is diluted to a content of approximately 5% by weight of 2-amino-5-methyl-phenol by direct expansion at 300° C. into water, or by pumping water into the autoclave after prior cooling to approximately 200° C. The resulting alkaline suspension of the K salt of 2-amino-5-methyl-phenol is metered into water at the same time as 36% by weight aqueous HCl at 90° C. at a pH of from 0.5 to 1.0. All the SO2 is expelled from the resulting, aqueous, approximately 4% by weight 2-amino-5-methyl-phenol hydrochloride solution using nitrogen or by applying a vacuum, the solution is if necessary clarified using activated carbon to remove tarry constituents, and the 2-amino-5-methyl-phenol is precipitated out by neutralization of the hydrochloric acid solution, for example using aqueous sodium hydroxide at a pH of from 4.5 to 6.0, and isolated in the usual manner, for example by filtration and washing with water.

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