Nitric oxide, also known as nitrogen oxide or nitrogen monoxide, is a colorless gas with the chemical formula NO. It is a free radical with an unpaired electron and is a heteronuclear diatomic molecule. It forms in combustion systems and can be generated by lightning in thunderstorms. Nitric oxide is a signaling molecule in many physiological and pathological processes, and it was proclaimed the "Molecule of the Year" in 1992. It should not be confused with nitrogen dioxide (NO2), a brown gas and major air pollutant, or nitrous oxide (N2O), an anesthetic gas.
Reactions with di- and triatomic molecules include dimerizing to dinitrogen dioxide, decomposing to elements, and forming nitrous acid (HNO2). In water, nitric oxide reacts with oxygen to form nitrous acid (HNO2), and with fluorine, chlorine, and bromine to form nitrosyl halides. The Traube reaction, discovered around 1898, remains of interest in nitric oxide prodrug research. Nitric oxide can also react directly with sodium methoxide, ultimately forming sodium formate and nitrous oxide by way of an N-methoxydiazeniumdiolate.
Coordination complexes of nitric oxide include terminal linear type (M−NO) and one-electron pseudohalide. In commercial settings, nitric oxide is produced by the oxidation of ammonia at 750–900 °C with platinum as catalyst in the Ostwald process. The uncatalyzed endothermic reaction of oxygen (O2) and nitrogen (N2), effected at high temperatures (>2000 °C) by lightning, has not been developed into a practical commercial synthesis.
Laboratory methods for nitric oxide generation include reduction of dilute nitric acid with copper, reduction of nitrous acid in the form of sodium nitrite or potassium nitrite, and the iron(II) sulfate route. NONOate compounds are also used for nitric oxide generation.
Detection and assay methods for nitric oxide include chemiluminescent reaction involving ozone, electroanalysis, and spin trapping of nitric oxide with iron-dithiocarbamate complexes. The most common compound is 4,5-diaminofluorescein (DAF-2).
The CAS Number of Nitric Oxide is 10102-43-9
The Molecular Formula of Nitric Oxide is NO
The Molecular Mass of Nitric Oxide is 30.01
The SMILES Notation of Nitric Oxide is [N]=O
The InChI Notation of Nitric Oxide is InChI=1S/NO/c1-2