Sulphur dioxide ions, decomposition

Acetamido - 3 - hydroxy -1 4- benzisoxazine - 6 - arsinic acid may be prepared by acetylation of the corresponding amino-acid, or by chloraeetylation in alkaline solution of 8-amino-6-acetamido-4-hydroxyphenylarsinic acid. It crystallises in colourless prisms, M.pt. 275° to 280° C. with decomposition, and forms amorphous barium and magnesium salts. Reduction with sulphur dioxide and potassium iodide yields 8-acetamido-3-h.ydro.vy-l h-benzisoxazine-6-dichloroarsine in tufts of white needles, which are converted to the arsenoxide by water. The oxide forms clusters of white needles, insoluble in water, sodium carbonate, or dilute mineral acids, soluble in dilute sodium hydroxide and in aji excess of ION ammonium hydroxide. 

It will be noted that the energy of activation is greatest in water, next in alcohol, and least in aniline, and it is probable that water tends to solvate more than alcohol, and alcohol to solvate more than aniline. These actual differences in the energies of activation can be attributed to heats of solvation which must be added to the energy of activation before decomposition can occur. The products chloroform and carbon dioxide are not solvated. It will be remembered that the trichloroacetic acid itself is completely stable, as shown by the failure to decompose in such solvents as carbon tetrachloride and sulphuric acid. This stabilizing of the trichloroacetate ion by the proton may be considered as a special limiting case towards which the stabilization by solvation can approach. 

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