Arsonoacetate

Z-Arginine hydrochloride, 12, 4 Arsanilic acid, 16, 85 Arsonoacetic acid, 10,108 Arylarsonic acid, preparation, IS, 59 y-Arylbutyric esters, 18, 25 Arylsulfur chlorides, preparation, 15, 45... 

An analogous mechanism is seen in the utilization of arsonoacetate by a bacterium as its sole source of energy and carbon (39). Arsenate is the product, and since the bacteria can oxidize arsenite, the original degradation of the arsonoacetate may be reductive and form arsenite, which is then oxidized to the less toxic arsenate. 

Fig. 13. Conceivable mechanism for the decarboxylation of arsonoacetic acids. When an arsonoacetic acid is boiled in propan-l-ol, and the propanol-water azeotrope is distilled off, the acid will be esterified completely on the arsono group but not on the carboxy group. Decarboxylation is observed.

This is easily done if R is propyl, because the azeotrope of water and propan-l-ol boils at a temperature well below the boiling point of the propanol, so one can distill off this azeotrope up a fractionating column until the temperature of the vapor reaches the boiling point of propanol. When this is done with an arsonoacetic acid, decarboxylation results. It may be that that hydron is involved, as shown in Fig. 13, since the reaction does not proceed if one starts with a monoanion of the arsonoacetic acid. 

In view of the ease with which water attacks an ester of arsenate in water, we wondered if carbon nucleophiles would similarly attack a trialkyl arsenate to form a C—As bond. We (Sparkes and Dixon, unpublished work) therefore treated the sodium salt of diethyl malonate with tripropyl arsenate, and hydrolyzed during workup. Some arsonoacetic acid was formed, but we have not found conditions that give a useful yield. 

The filtrate is poured into a solution containing 185 g. of crystallized barium chloride dissolved in 600 cc. of hot water. Barium arsonoacetate, Ba(02CCH2As03Ba)2 (hydrated), forms a thick, finely divided precipitate. The mixture is stirred for several minutes and then allowed to stand until the following day, when it is filtered upon a 15-cm. Buchner funnel and washed... 

Sodium arsonoacetate is prepared by adding the freshly filtered and washed barium arsonoacetate as obtained above (without drying) to a solution of 108 g. of anhydrous sodium sulfate in 500 cc. of hot water. The mixture is mechanically stirred for one hour, the barium sulfate filtered off, and the filtrate concentrated on the steam bath until crystallisation commences. Upon cooling and stirring (Note 3), sodium arsonoacetate separates and is filtered by suction, the filtrate being concentrated to obtain a second crop of crystals. The yield of the combined fractions is 100-110 g. (80-88 per cent of the theoretical amount). 

A solution of 12.5 g. of sodium arsonoacetate and 30 g. of sodium hypophosphite (NallyPOa-HaO) in 150 cc. of cold 15 per cent sulfuric acid is allowed to stand at room temperature. After two or three days, the yellow precipitate is filtered off, washed with water, and dried in a vacuum over sulfuric acid or phosphorus pentoxide. A second crop is obtained by allowing the mother liquid to stand for two days longer. 

Arsonoacetic acid was obtained by Ehrlich and Bertheim 1 by treating -aminophenylarsenoacetic acid with bromine. It has been prepared by the action of three molecular equivalents of sodium chloroacetate on two of sodium arsenite, followed by isolation as the calcium salt,2 but it is found that these proportions are less satisfactory than the ones adopted.3 Arseno-acetic acid has been prepared recently by Palmer.3... 

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