What Is Nitrogen Monoxide?
Nitrogen monoxide, commonly known as nitric oxide, is an inorganic compound consisting of nitrogen and oxygen with the formula NO. It is a colorless, odorless gas at standard temperature and pressure.
Nitrogen monoxide can be synthesized in several ways, including the reaction of metals like copper with dilute nitric acid, or by the reaction of nitrogen dioxide with sulfur dioxide. In the laboratory, it is often collected using the water displacement method due to its insolubility in water.
Uses of Nitrogen Monoxide
In biological systems, nitric oxide plays a crucial role. It helps regulate blood pressure by signaling smooth muscle relaxation in blood vessels, thus preventing atherosclerosis. The body’s production of nitric oxide decreases with age. However, it can be increased through moderate exercise and dietary intake of arginine.
Nitrogen monoxide also finds applications in materials science, for instance, in detecting radicals on polymer surfaces using X-ray photoelectron spectroscopy.
Properties of Nitrogen Monoxide
Nitrogen monoxide has a melting point of -262.5 °F (-163.6 °C) and a boiling point of -241 °F (-151.7 °C). It rapidly oxidizes in the presence of oxygen to form nitrogen dioxide (NO2). It reacts with water to produce nitrous acid (HNO2) and with halogens to yield nitrosyl halides, such as nitrosyl chloride when combined with chlorine. When nitrogen monoxide reacts with nitrogen dioxide, it forms dinitrogen trioxide, which has a dark blue color.
As an oxide of nitrogen, the oxidation state of nitrogen in NO is +2. The nitrogen atom has an unpaired electron, making NO paramagnetic. Its molecular weight is 30.0061 g/mol, and the N-O bond length is 115 pm.
Other Information on Nitrogen Monoxide
1. Synthesis of Nitrogen Monoxide by the Ostwald Process
Nitrogen monoxide is industrially produced via the Ostwald process, which involves heating ammonia to about 1652 °F (900 °C) in the presence of a platinum-rhodium catalyst. This method yields nitrogen monoxide with high efficiency (95-98%).
2. Environmental Impact of Nitrogen Monoxide
Nitrogen monoxide is a contributor to air pollution as part of the nitrogen oxides (NOx) group. It reacts with water vapor to form nitric acid, contributing to acid rain. Nitrogen monoxide is produced naturally by lightning and wildfires, but also through human activities like burning fossil fuels. In the atmosphere, it is involved in the formation of photochemical smog through its oxidation to nitrogen dioxide and subsequent reactions leading to ozone and other oxidants.
3. Metal Complexes With Nitrogen Monoxide
Nitrogen monoxide forms complexes with transition metals, known as metal nitrosyls (M-NO). The M-N-O bond angle in these complexes typically ranges between 120° and 140°.