Hydroxylamine-O-sulfonic acid

white to slightly beige crystalline powder

Hydroxylamine-O-sulfonic acid is used in the synthesis of quinolones for the benzodiazepine site of GABAA receptors. It is also used as a polymerization catalyst and an amination reagent. It is involved in the preparation of diazene by reacting with an alkali. It is also used in the inhibition of polychlorinated dibenzo-p-dioxins (PCDD) as well as (polychlorinated biphenyl) PCB formation in co-combustion.

Hydroxylamine-O-sulfonic acid (HOSA) may be used to synthesize (Z)-1H-purin-6(7H)-ylideneaminooxysulfonic acid.
HOSA may be used as an aminating reagent in the synthesis of:

• 1-aminotetrazoles and 2-aminotetrazoles
• N-aminopiperidine (NAPP)
• 1H,1′ H-2,2′-biimidazole-1,1′-diamine

Hydroxylamine-O-sulfonic acid is a versatile synthetic reagent. It is widely employed as a nucleophile and as an electrophile in various organic syntheses. It can be synthesized by reacting hydroxylamine sulfate with 30% fuming H₂SO₄.

63 ml of 20~25% fuming sulfuric acid was slowly added dropwise to 16.4 g of hydroxylamine sulfate under mechanical stirring. The temperature was controlled below 60°C, and the time of dropwise addition was 40~60 minutes. After the dropwise addition, the temperature was raised to 60°C and the reaction was continued with stirring for 2~3 hours. Cool to 10°C and stir for 1 hour, then drop 100ml of ethyl acetate. The concentrated solution was allowed to stand for half an hour, separated and rapidly filtered. The crude product was washed with ethyl acetate and dried under vacuum to yield 21.5 g of hydroxylamine-O-sulfonic acid (95% yield). The product was stored on P2O6 in a vacuum desiccator. The purity of the product was 87.69%.

Stir the solid vigorously with anhydrous Et2O and filter it off using large volumes of dry Et2O. Drain dry at the pump for 5minutes and then for 12-14hours in a vacuum. Store it in a vacuum desiccator over conc H2SO4. Determine the purity by oxidation of iodide to I2. It must be stored in a dry atmosphere at 0-4o. It decomposes slowly in H2O at 25o and more rapidly above this temperature. [Matsuguma & Andrieth Inorg Synth V 122 1957.]