Nitrosylsulfuric acid is the

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the formula . It is a colourless solid that is used industrially in the production of

caprolactam Caprolactam (CPL) is an organic compound with the formula (CH2)5C(O)NH. This colourless solid is a lactam (a cyclic amide) of caproic acid. Global demand for this compound is approximately five million tons per year, and the vast majority is us ...

, and was formerly part of the lead chamber process for producing

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular fo ...

. The compound is the mixed anhydride of sulfuric acid and

nitrous acid Nitrous acid (molecular formula ) is a weak and monoprotic acid known only in solution, in the gas phase and in the form of nitrite () salts. Nitrous acid is used to make diazonium salts from amines. The resulting diazonium salts are reagent ...

. In organic chemistry, it is used as a reagent for nitrosating, as a diazotizing agent, and as an

oxidizing agent An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxi ...

Synthesis and reactions

A typical procedure entails dissolving

sodium nitrite Sodium nitrite is an inorganic compound with the chemical formula NaNO2. It is a white to slightly yellowish crystalline powder that is very soluble in water and is hygroscopic. From an industrial perspective, it is the most important nitrite ...

in cold sulfuric acid: : It can also be prepared by the reaction of

nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available ni ...

and

sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic a ...

. This procedure generates the nitrosylsulfuric acid as an intermediate en route to NOCl. is used in

organic chemistry Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J ...

to prepare diazonium salts from

amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent ...

s, for example in the

Sandmeyer reaction The Sandmeyer reaction is a chemical reaction used to synthesize aryl halides from aryl diazonium salts using copper salts as reagents or catalysts. It is an example of a radical-nucleophilic aromatic substitution. The Sandmeyer reaction provide ...

. Related NO-delivery reagents include

nitrosonium tetrafluoroborate Nitrosonium tetrafluoroborate, also called nitrosyl tetrafluoroborate, is a chemical compound with the chemical formula NOBF4. This colourless solid is used in organic synthesis as a nitrosating agent. NOBF4 is the nitrosonium salt of fluorob ...

and

nitrosyl chloride Nitrosyl chloride is the chemical compound with the formula NOCl. It is a yellow gas that is commonly encountered as a component of aqua regia, a mixture of 3 parts concentrated hydrochloric acid and 1 part of concentrated nitric acid. It is a ...

. In industry, the nitrosodecarboxylation reaction between nitrosylsulfuric acid and

cyclohexanecarboxylic acid Cyclohexanecarboxylic acid is the organic compound with the formula C6H11CO2H. It is the carboxylic acid of cyclohexane. It is a colorless oil that crystallizes near room temperature.. Preparation and reactions It is prepared by hydrogenation ...

is used to generate caprolactam: : Nitrosodecarboxylation_Caprolactam_Synthesis

Safety

Nitrosylsulfuric acid is a hazardous material and precautions are indicated.

References

{{Hydrogen compounds Acid anhydrides Acids Hydrogen compounds Nitrosyl compounds Sulfate esters Sulfur oxoacids Nitrogen(III) compounds