Nitrosyl perchlorate

Nitrosyl perchlorate is the inorganic compound with the formula NO(ClO4). A hygroscopic white solid, it is the salt of the nitrosonium cation with the perchlorate anion. It is an oxidant and strong electrophile, but has fallen out of use with the availability of the closely related salt nitrosonium tetrafluoroborate NO(BF4).

Preparation
Nitrosyl perchlorate was first produced in 1909 by passing dinitrogen trioxide gas into concentrated perchloric acid:
 * N2O3 + 2 HClO4 → 2 NOClO4 + H2O

It can also be prepared by passing dinitrogen trioxide gas into a mixture of sodium perchlorate and sulfuric acid. A much purer product can be produced by reacting dichlorine heptoxide with anhydrous nitric acid.

Structure
The structure of NOClO4 has not been elucidated by X-ray crystallography. However, the Raman spectroscopy of NOClO4 suggests that nitrosyl perchlorate consists of distinct NO+ and ClO4– ions.

Properties
Nitrosyl perchlorate decomposes at 100 °C to nitronium perchlorate, which then subsequently decomposes into chlorine and nitrogen oxides.

This compound hydrolyzes in water to form nitrous acid and perchloric acid:
 * NOClO4 + H2O → HNO2 + HClO4

With a strong base, such as sodium hydroxide, it produces perchlorate, nitrite, nitrate, nitric oxide, and water. This reaction was used to calculate the heat of formation of nitrosyl perchlorate. As a strong oxidizer, nitrosyl perchlorate reacts explosively with various organic compounds, such as ethanol, acetone, ether, and aniline.

Uses
Nitrosyl perchlorate is used in the laboratory as a perchlorating agent. Although it has been investigated as a potential rocket propellant, it has not been commercialized.