Imidodisulfuric acid, N-hydroxy-, sodium salt (1:2)

In a 5-liter flask equipped with an efficient stirrer and surrounded with a large ice-salt bath is placed 4-liters of distilled water, 325gm (3 moles) of anhydrous sodium carbonate, and 420 gm (5.8 moles) of 95% pure sodium nitrite. The mixture is stirred and cooled. When the temperature has reached -5°C, sulfur dioxide is passed into the solution at such a rate that the solution temperature never exceeds 0°C. With efficient cooling, the reduction is completed in approximately 4 hr. The end of the reduction is indicated by a drop in the pH of the solution to the acid side. Just before the reaction turns acid, the solution becomes slightly brown in color. The solution is approximately 1.2 Μ in sodium hydroxylamine disulfonate and may be used directly for the preparation of oximes. In using sodium hydroxylamine disulfonate, the reagent is treated with a carbonyl compound, warmed, and cooled. Only at this point is the reaction mixture neutralized with an alkaline solution. This method is suitable for the preparation of a range of carbonyl compounds. Negative results were obtained in the case of benzil and quinone monoxime, either because the oximes are not sufficiently soluble in the reaction medium or because the oximes produced are not stable in the acidic reaction solution.