Production
NH2OH can be produced via several routes. The main route is via Raschig synthesis: aqueous ammonium nitrite is reduced by HSO4− and SO2 at 0°C to yield a hydroxylamido-N,N-disulfate anion:
- NH4NO2 + 2 SO2 + NH3 + H2O → 2 NH4+ + N(OH)(OSO2)22−
This anion is then hydrolyzed to give (NH3OH)2SO4:
- N(OH)(OSO2)22− + H2O → NH(OH)(OSO2)− + HSO4−
- 2 NH(OH)(OSO2)− + 2 H2O → (NH3OH)2SO4 + SO2−
4
Solid NH2OH can be collected by treatment with liquid ammonia. Ammonium sulfate, (NH4)2SO4, a side-product insoluble in liquid ammonia, is removed by filtration; the liquid ammonia is evaporated to give the desired product.
The net reaction is: 2NO−
2 + 4SO2 + 6H2O + 6NH3 → 4SO2−
4 + 6NH+
4 + 2NH2OH
Hydroxylammonium salts can then be converted to hydroxylamine by neutralization:
- (NH3OH)Cl + NaOBu → NH2OH + NaCl + BuOH
Hydroxylamine can also be produced by the reduction of nitrous acid or potassium nitrite with bisulfite:
- HNO2 + 2 HSO3− → N(OH)(OSO2)22− + H2O → NH(OH)(OSO2)− + HSO4−
- NH(OH)(OSO2)− + H3O+ (100°C/1 h) → NH3(OH)+ + HSO4−
Read more about this topic: Hydroxylamine
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