Acidification Activated carbon filtration, dissolved

A suspension of 27.5 g. (0.20 mole) of the crude nitroso compound in 200 ml. of a mixture of 1 part of concentrated nitric acid to 3 parts of water is agitated and cooled over a period of 3 hours. The solid is filtered off, washed with water, and dissolved in 5 sodium hydroxide solution. The alkaline solution is heated with activated carbon, the resulting mixture filtered, and the filtrate treated with excess lO o hydrochloric acid by dropwise addition of the acid. External cooling is used during the acidification. The 2-methyl-4-nitro-phenol is precipitated in an overall yield of 82. The product melts at 91°. 

A mixture of 15 g. (0.1 mole) of isatin [Org. Syntheses Coll. Vol. 1, 327 (1941)], 22.5 g. (0.19 mole) of acetophenone, 120 ml, of absolute ethanol, and 60 ml. of 33% aqueous potassium hydroxide solution is refluxed for 6 hours. The ethanol and most of the excess acetophenone are then removed by heating in an evaporating dish. The residue is dissolved in water, the resulting solution is extracted with ether, filtered, and acidified slowly with dilute hydrochloric acid with cooling. After 12 hours standing, the precipitated solid is dissolved in sodium carbonate solution and diluted to 750 ml., 50 g. of sodium chloride is added, and the solution is allowed to stand for 36 hours. The precipitated material is removed by filtration, and the acid is precipitated by careful acidification of the filtrate with dilute hydrochloric acid. An excess of hydrochloric acid should be avoided. The acid is recrystallized twice from absolute ethanol with activated carbon treatment it consists of 16.5 g. (65%) of yellow needles, m.p. 208-209°. 

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