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|Section2= |Section3= |Section5= |Section6= |Section7= |Section8= }} Nitric oxide (nitrogen oxide,〔IUPAC nomenclature of inorganic chemistry 2005. (PDF ).〕 nitrogen monoxide) is a molecular, chemical compound with chemical formula of NO that is a colorless gas under standard conditions. Nitric oxide is a free radical—i.e., its bonding structure includes an unpaired electron—and it is in the class of heteronuclear diatomic molecules that are of historic theoretical interest (for the insights they gave in formulating early modern theories of bonding). It is a practically important intermediate in the chemical industry. In addition, some is unavoidably produced during combustion of fossil fuels in power plants and automobile engines, with excess being created when there is present more air, or higher temperatures, than needed for efficient and complete combustion of the fuel. It is also produced naturally by the extremely high air temperatures produced along the path of lightning in thunderstorms. In mammals including humans, NO is an important cellular signaling molecule involved in many physiological and pathological processes. It is a powerful vasodilator with a short half-life of a few seconds in the blood. Long-known pharmaceuticals such as nitroglycerine and amyl nitrite were found to be precursors to nitric oxide more than a century after their first use in medicine. Low levels of nitric oxide production are important in protecting organs such as the liver from ischemic damage. Despite being a simple molecule, NO is an important biological regulator and is therefore a fundamental component in the fields of neuroscience, physiology, and immunology. It was proclaimed "Molecule of the Year" in 1992. Research into its function led to the 1998 Nobel Prize for discovering the role of nitric oxide as a cardiovascular signalling molecule. Nitric oxide should not be confused with nitrous oxide (N2O), an anaesthetic, or with nitrogen dioxide (NO2), a brown toxic gas and a major air pollutant, the latter being a product to which nitric oxide is rapidly oxidised in air. ==Reactions== *When exposed to oxygen, NO is converted into nitrogen dioxide. :: 2 NO + O2 → 2 NO2 :This conversion has been speculated as occurring via the ONOONO intermediate. In water, NO reacts with oxygen and water to form HNO2 or nitrous acid. The reaction is thought to proceed via the following stoichiometry: :: 4 NO + O2 + 2 H2O → 4 HNO2 *NO will react with fluorine, chlorine, and bromine to form the XNO species, known as the nitrosyl halides, such as nitrosyl chloride. Nitrosyl iodide can form but is an extremely short-lived species and tends to reform I2. :: 2 NO + Cl2 → 2 NOCl *Nitroxyl (HNO) is the reduced form of nitric oxide. * Nitric oxide dimer N2O2 is formed when nitric oxide is cooled. *Nitric oxide reacts with acetone and an alkoxide to a ''diazeniumdiolate'' or ''nitrosohydroxylamine'' and methyl acetate: : :This reaction was discovered around 1898, and remains of interest today in NO prodrug research. Nitric oxide can also react directly with sodium methoxide, forming sodium formate and nitrous oxide. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Nitric oxide」の詳細全文を読む スポンサード リンク
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