Trioxidonitrogen(•) or nitrate radical is an

oxide An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the E ...

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

with formula , consisting of three

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

atoms covalently bound to a nitrogen atom. This highly unstable blue compound has not been isolated in pure form, but can be generated and observed as a short-lived component of gas, liquid, or solid systems. Like

nitrogen dioxide Nitrogen dioxide is a chemical compound with the formula . It is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year for use primarily in the producti ...

, it is a

radical Radical may refer to: Politics and ideology Politics *Radical politics, the political intent of fundamental societal change *Radicalism (historical), the Radical Movement that began in late 18th century Britain and spread to continental Europe and ...

(a molecule with an unpaired

valence electron In chemistry and physics, a valence electron is an electron in the outer shell associated with an atom, and that can participate in the formation of a chemical bond if the outer shell is not closed. In a single covalent bond, a shared pair forms ...

), which makes it

paramagnetic Paramagnetism is a form of magnetism whereby some materials are weakly attracted by an externally applied magnetic field, and form internal, induced magnetic fields in the direction of the applied magnetic field. In contrast with this behavior, d ...

. It is the uncharged counterpart of the

nitrate Nitrate is a polyatomic ion A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

and an

isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Iso ...

of the peroxynitrite radical . Nitrogen trioxide is an important intermediate in reactions between atmospheric components, including the destruction of

ozone Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...

.R. P. Wayne, I. Barnes, P. Biggs, J. P. Burrows, C. E. Canosa-Mas, J. Hjorth, G. Le Bras. G. K. Moortgat, D. Perner, G. Poulet, G. Restelli, and H. Sidebottom (1991): "The nitrate radical: Physics, chemistry, and the atmosphere". ''Atmospheric Environment. Part A. General Topics''. volume 25, issue 1, pages 1-203. Richard A. Graham and Harold S. Johnston (1978): "The photochemistry of the nitrate radical and the kinetics of the nitrogen pentoxide-ozone system". ''Journal of Physical Chemistry'', volume 82, issue 3, pages 254-268.

History

The existence of the radical was postulated in 1881-1882 by Hautefeuille and Chappuis to explain the absorption spectrum of air subjected to a silent electrical discharge.

Structure and properties

The neutral molecule appears to be planar, with three-fold rotational symmetry (symmetry group ''D''_3''h''); or possibly a

resonance Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillatin ...

between three Y-shaped molecules. The radical does not react directly with water, and is relatively unreactive towards closed-shell molecules, as opposed to isolated atoms and other radicals. It is decomposed by light of certain wavelengths into

nitric oxide Nitric oxide (nitrogen oxide or nitrogen monoxide) is a colorless gas with the formula . It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its che ...

and oxygen . The absorption spectrum of has a broad band for light with

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...

s from about 500 to 680 nm, with three salient peaks in the

visible Visibility, in meteorology, is a measure of the distance at which an object or light can be seen. Visibility may also refer to: * A measure of turbidity in water quality control * Interferometric visibility, which quantifies interference contrast ...

at 590, 662, and 623 nm. Absorption in the range 640–680 nm does not lead to dissociation but to

fluorescence Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...

: specifically, from about 605 to 800 nm following excitation at 604.4 nm, and from about 662 to 800 nm following excitation at 661.8 nm. In water solution, another absorption band appears at about 330 nm (

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...

). An excited state can be achieved by photons of wavelength less than 595 nm.

Preparation

Nitrogen trioxide can be prepared in the gas phase by mixing nitrogen dioxide and ozone: : + → + This reaction can be performed also in the solid phase or water solutions, by irradiating frozen gas mixtures,

flash photolysis Flash photolysis is a pump-probe laboratory technique, in which a sample is first excited by a strong pulse of light from a pulsed laser of nanosecond, picosecond, or femtosecond pulse width or by another short-pulse light source such as a fla ...

and

radiolysis Radiolysis is the dissociation of molecules by ionizing radiation. It is the cleavage of one or several chemical bonds resulting from exposure to high-energy flux. The radiation in this context is associated with ionizing radiation; radiolysis is ...

of nitrate salts and nitric acid, and several other methods. Nitrogen trioxide is a product of the

photolysis Photodissociation, photolysis, photodecomposition, or photofragmentation is a chemical reaction in which molecules of a chemical compound are broken down by photons. It is defined as the interaction of one or more photons with one target molecule. ...

dinitrogen pentoxide Dinitrogen pentoxide is the chemical compound with the formula , also known as nitrogen pentoxide or nitric anhydride. It is one of the binary nitrogen oxides, a family of compounds that only contain nitrogen and oxygen. It exists as colourless ...

chlorine nitrate Chlorine nitrate, with chemical formula ClNO3 is an important atmospheric gas present in the stratosphere. It is an important sink of chlorine that contributes to the depletion of ozone. It explosively reacts with metals, metal chlorides, alcohol ...

, and

peroxynitric acid Peroxynitric acid or peroxonitric acid is a chemical compound with the chemical formula, formula . It is an oxyacid of nitrogen, after peroxynitrous acid. Preparation Peroxynitrate, the conjugate base of peroxynitric acid, is formed rapidly duri ...

{{chem, HO, 2, NO, 2 and its salts. :N₂O₅ → NO₂ + NO₃ :2 ClONO₂ → Cl₂ + 2 NO₃

References

Nitrogen oxides Free radicals