Arsonophenoxyacetic Acid

In a 2-1. round-bottom flask is placed 218 g. (1 mole) of p-hydroxyphenylarsonic acid (Note 1) and 375 cc. of water. A solution of 180 g. (4.5 moles) (Note 2) of sodium hydroxide in 375 cc. of water is added, and the mixture shaken until a homogeneous solution is obtained. After cooling to 40-50° there is added 189 g. (2 moles) of chloroacetic acid in small portions (Note 3) with stirring, and the clear solution is refluxed for four hours. At the end of this time the mixture is cooled to 20°, filtered to remove a slight flocculent precipiLaLe, and the -arsonophenoxyacetic acid precipitated (Note 4) by the addition of 200 cc. (2.1 moles) of hydrochloric acid (sp. g. 1.19). The product is filtered on a 10-cm. Buchner funnel and washed with three successive 100-cc. portions of cold water. It is then crystallized from 2 1. of hot water (Note 5), filtered, and washed 

Commercial phenolarsonic acid may be used, or 240 g. of sodium -hydroxyphenylarsonate (Org. Syn. 4, 65) and 140 g. of sodium hydroxide may be substituted for the acid and the larger amount of base. 

The use of less than 4.5 moles of alkali lowers the yield, while an increase in the alkali concentration does not increase the yield. 

Unless the chloroacetic acid is added cautiously, there may be a violent reaction and the yield of / -arsonophenoxyacetic acid is lowered. 

The product sometimes does not precipitate readily without vigorous agitation and rubbing the inside wall of the vessel with a stirring rod. 

---

The odor of phenol is strong at the end of the reaction, but most of the />-hydroxyphenylarsonic acid which does not react with the chloroacetic acid is not hydrolyzed and can be recovered in the filtrate from the />-arsonophenoxyacetic acid. 

Arsonophenoxyacetic acid has been made by heating aqueous sodium -hydroxyphenylarsonate, two moles of chloroacetic acid, and four moles of sodium hydroxide.1... 

---