Nitrosylsulfuric acid

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Nitrosylsulfuric acid
Structural formula of nitrosylsulfuric acid
Ball-and-stick model
CAS number 7782-78-7 YesY
PubChem 82157
ChemSpider 74147 YesY
Jmol-3D images Image 1
Molecular formula HNO5S
Molar mass 127.08 g/mol
Appearance pale yellow crystals
Density 1.612 g/mL in
40% sulfuric acid soln
Melting point 73.5 °C
Boiling point decomposes
Solubility in water decomposes
Solubility soluble in H2SO4
Main hazards oxidizer
Related compounds
Other anions NOCl
Other cations NaHSO4
Related compounds NOBF4
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Nitrosylsulfuric acid is the chemical compound with the formula NOHSO4. It is a colourless solid that is used industrially in the production of caprolactam.[1]

Synthesis and reactions[edit]

A typical procedure entails dissolving sodium nitrite in concentrated sulfuric acid in an ice bath:[2][3]

HNO2 + H2SO4 → NOHSO4 +H2O

The molecule can also be viewed as the mixed acid anhydride of sulfuric acid and nitrous acid. Alternatively, it can be prepared by the reaction of nitric acid and sulfur dioxide.[4]

NOHSO4 is useful in organic chemistry to prepare diazonium salts from amines. Related NO-delivery reagents include nitrosonium tetrafluoroborate ([NO]BF4) and nitrosyl chloride.


  1. ^ Ritz, J.; Fuchs, H.; Kieczka, H.; Moran, W. C. (2002). "Caprolactam". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a05_031. 
  2. ^ Hodgson, H. H.; Mahadevan, A. P.; Ward, E. R. (1955), "1,4-Dinitronaphthalene", Org. Synth. ; Coll. Vol. 3: 341  (diazodization followed by treatment with nitrite)
  3. ^ Sandin, R. B.; Cairns, T. L. (1943), "1,2,3-Triiodo-5-nitrobenzene", Org. Synth. ; Coll. Vol. 2: 604  (diazodization followed by treatment with iodide)
  4. ^ Coleman, G. H.; Lillis, G. A.; Goheen, G. E. (1939). "Nitrosyl Chloride". Inorganic Syntheses 1: 55–59. doi:10.1002/9780470132326.ch20.  This procedure generates the nitrosylsulfuric acid as an intermediate en route to NOCl.