Dioxide nitrogen

Nitrogen Dioxide.—To nitrogen dioxide we assign the resonating structure 

The nitronium cation, NO, with a structure resembling that of carbon dioxide (linear, N—O = 1.154 A), was discovered by spectroscopic methods.26 Its linear configuration has been verified for NO2CIO4 by spectroscopic methods28 and for NO NO (crystalline dinitrogen pentoxide) by x-ray diffraction,27 and also for several other crystals.28 

Dinitrogen Tetroxide.—The dimer of nitrogen dioxide is not very stable its enthalpy of formation from the monomer is 13.873 kcal/mole. The molecule is found in both the crystal (x-ray diffraction)29 and the gas (electron diffraction)80 to be planar, with orthorhombic symmetry. The N—N bond length reported for the crystal is 1.64 A. The value for the gas molecule, 1.75 A, is probably somewhat more accurate.81 This value is 0.28 A greater than the single-bond value found for hydrazine the bond number of the bond is accordingly about 0.34 (Equation 7-7). 

The explanation of this weak bond is provided by the stability of the three-electron bonds in the NO molecules that compose the dimer, which strive to prevent the two odd electrons from settling down on the 

91 The ONO angle is reported in the x-ray study as 108°. It is highly probable, as discussed above, that the electron-diffraction value 133.7° is correct. If the atoms are moved from their reported positions in the crystal by minimum amounts (weighted by inverse of scattering power for x-rays) to achieve this value of the angle, the N—N distance becomes 1.74 A, agreeing with the electron-diffraction value. 

Synonyms Dinitrogen tetroxide, nitrogen peroxide, and nitrogen tetroxide 

HI / Individual Compressed Gases and Mixtures U.S. Units SI Units 

Nitrogen dioxide is available in grades of 99.5 percent or 99.995 percent. 

A major hazard regarding exposure to nitrogen dioxide is that serious effects are not 

Exposures to nitrogen dioxide of 10 minutes or less at a level of about 150 ppm produces cough, nose and throat irritation, tearing, headache, nausea, and vomiting. Exposures ranging from 50-150 ppm have been associated with moderate irritation to the eyes and mucous membranes. Permanent eye damage can occur, however, if exposures at these levels are prolonged. [6] 

Small amounts of nitrogen dioxide are present naturally in the atmosphere as the result of lightning strikes, volcanic action, forest fires, and bacterial action on dead plants and animals. Much larger amounts are present because of human activities, primarily the combustion of fossil fuels, such as coal and petroleum products. 

Nitrogen dioxide. Red atoms are oxygen and blue atom is nitrogen. Gray stick indicates a double bond, publishers RESOURCE CROUP 

Nitrogen dioxide occurs naturally when nitric oxide (NO) is oxidized in the atmosphere. Nitric oxide forms naturally whenever sufficient energy is available to make possible the reaction between nitrogen and oxygen, the two primary components of the atmosphere. The formula for this reaction is 

Nitric oxide, in turn, reacts readily with oxygen to form nitrogen dioxide. This reaction can be shown as 

The amount of nitrogen dioxide produced naturally is so small that the gas s distinctive brown color is unnoticeable. 

As is well known, nitrogen dioxide exists as the dimer N204, at low temperatures, and as the monomer, N02, at high temperatures. Its boiling point is 21°C, and its density at 0°C d = 1.49 g/cm3. 

On the basis of the observation that the addition of nitrogen dioxide to compounds with double bonds yields not only nitro compounds, but nitrous acid esters as well (p. 99). Schaarschmidt [38a,39,40] expressed the view that nitrogen dioxide exists in three forms which are in equilibrium. This may be represented in modem symbols in the following way  

More recent thermochemical studies (Giauque and Kemp [41]), and spectral work (Millen [42]), as well as determination of the dielectric constant (Addison and Lewis [43]), indicate that formula (b) seems to be the most probable. Formula (d) is possible, but less probable. 

The stereo-structure, including bond distances and bond angles of vapour phase N02 (Fig. 17), was investigated by Maxwell and Mosley [44] in 1940 by electron 

N204 in nitric acid solutions dissociated in the same way, as Goulden and Millen [47] found, when examining Raman spectra of such solutions. 

LABORATORY CHEMICAL SAFETY SUMMARY NITROGEN DIOXIDE  

Physical Properties Yellow-brown liquid to reddish brown gas generally a mixture of NO2 and N2O4 (at - 11 °C liquid is 0.01% NOj, at 21 °C hquid is 0.1% NO2 and gas is 15.9% NOj) bp 21 °C, mp -11 °C Miscible in aU proportions with water reacting to form nitric and nitrous acids 

Major Hazards Highly toxic by inhalation high concentrations of the gas and hquid NO2-N2O4 are corrosive to the skin, eyes, and mucous membranes. 

Nitrogen dioxide is not combustible (NFPA rating = 0) but is a strong oxidizing agent and will support combustion. Cylinders of NO2 gas exposed to fire or intense heat may vent rapidly or explode. 

Nitrogen dioxide-nitrogen tetroxide is a powerful oxidizer and can cause many organic substances to ignite. This substance may react violently with alcohols, aldehydes, acetonitrile, DMSO, certain hydrocarbons, and chlorinated hydrocarbons. Metals react vigorously and alkali metals ignite in NO2. 

Short-term exposures of rats to a concentration of 0.5 ppm of nitrogen dioxide for 4 hours or to 1 ppm for one hour were sufficient to induce reversible histological changes in the lung [26]. In the lung of rats killed 

During the exposure of rabbits for 4 hours daily for six days to 0.25 ppm of nitrogen dioxide, structural changes in the lung collagen were observed, via electron microscopy [27]. These changes were observable even 7 days after terminating the exposure, which indicates slow recovery. 

An emphysema-like damage to the lung occurs after chronic exposures to nitrogen dioxide. 

Emphysema-like lesions were also observed in the lungs of beagle dogs exposed to 25 ppm of nitrogen dioxide for six months [28]. 

Nitrogen dioxide, similarly to ozone, can induce lipidic peroxidation, which can be demonstrated after a 4-hour exposure to 1 ppm in rat lung lipidic extracts [32]. The maximal peroxidation was observed 24 hours 

Similar effects were found on absorption into aqueous sodium hydroxide solutions. 

FIGURE 4.11 High-resolution (0.003 nm) absorption spectrum of N02 at room temperature (adapted from Harder et al., 1997). 

Hygienic Guide Series Nitroethane. Akron, OH, Am Ind Hyg Assoc, 1978 

Dayal R, Gescher A, Harpur ES, et al Comparison of the hepatotoxicity in mice and the mutagenicity of three nitroalkanes. Fundam Appl Toxicol 13 341-348, 1989 

Anonymous Nitroethane A 4-Day and 13-Week Inhalation Study in Rats and Mice. EPA/OTS Doc No. 86-890001191, NTIS/OTS0520703, Environmental Protection Agency, 2000 

Uses/Sources. Intermediate in nitric and sulfuric acid production nitration of organic compounds and explosives found in vehicle emissions and fossil fuel combustion 

Toxicology. Nitrogen dioxide is a respiratory irritant at high concentrations it causes pulmonary edema and, rarely among survivors, bronchiolitis obliterans. 

2-Dinitroethane and 1,2-dinitrocyclohexane can be formed in this way from the corresponding alkenes in 42 % and 37 % yield respectively.  

The addition of dinitrogen tetroxide across the double bonds of electron deficient fluorinated alkenes is a particularly useful route to v/c-dinitro compounds where yields are frequently high 8,37 tetrafluoroethylene gives a 53 % yield of l,2-dinitro-l,l,2,2-tetrafluoroethane.  

The reaction of a-nitroalkenes with nitrogen dioxide or its dimer, dinitrogen tetroxide, has been used to synthesize polynitroalkanes. Thus, the reaction of dinitrogen tetroxide with 2,3-dinitro-2-butene (6) and 3,4-dinitro-3-hexene is reported to yield 2,2,3,3-tetranitrobutane (7, 25 %) and 3,3,4,4-tetranitrohexane (32 %) respectively.  

The reaction of alkenes with nitrogen oxides and other nitrating agents have been extensively discussed by Olah, Topchiev, and in numerous reviews.  

The reaction of alkynes with dinitrogen tetroxide is less synthetically useful as a route to nitro compounds. The reaction of 3-hexyne with dinitrogen tetroxide yields a mixture of cis- and fran -3,4-dinitro-3-hexene (4.5% and 13% respectively), 4,4-dinitro-3-hexanone (8%), 3,4-hexanedione (16%) and propanoic acid (6%). 2-Butyne forms a mixture containing both cis- and fran -2,3-dinitro-2-butene (7 % and 34 % respectively).  

The photodissociation of NO2 at 337 nm (N2 laser) has been studied by Zacharias et al. (91) with a tunable probe laser near 235 nm to detect NO by LIF using its A2E+ - X n transition. 

The absorption and fluorescence cross sections of NO2 have been measured by Lee and Chiang (95) in the 106-162 nm region. 

The conversion of NO2 to nitric acid [equation (7)] has been much studied as the rate-determining step in the industrial manufacture of nitric 

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Electrons are shared when nitrogen monoxide combines with oxygen, a spontaneous reaction, to give nitrogen dioxide... 

The structure of nitrogen dioxide contains an unpaired (odd) electron and the molecule is consequently paramagnetic. The odd electron is not localised on any atom and the structure can be best represented as a resonance hybrid of the structures ... 

Unlike nitrogen monoxide, nitrogen dioxide has properties more typical of an odd electron molecule. It is a coloured (brown), reactive gas which dimerises to the diamagnetic colourless gas dinitrogen tetroxide, N2O4. in which the odd electron is paired. The structure of dinitrogen tetroxide can be represented as a resonance hybrid of ... 

Nitrogen dioxide is prepared by heating the nitrate of a heavy metal, usually that of lead(ll) ... 

If the mixture of oxygen and nitrogen dioxide is passed through a U tube in a freezing mixture the dioxide condenses mainly as N2O4 and the oxygen passes on. 

Nitrogen dioxide dissolves in water to give a mixture of nitrous and nitric acids ... 

If this reaction takes place in air, the evolved nitrogen monoxide is oxidised to the dioxide and this dissolves again as in equation (9.1) hence virtually complete conversion of nitrogen dioxide to nitric acid can occur (see nitric acid, below). With alkalis, a mixture of nitrite and nitrate is formed ... 

The nitrates of other metals give nitrogen dioxide, oxygen and the metal oxide, unless the latter is unstable to heat, in which case the metal and oxygen are formed (for example from nitrates of silver and mercury) ... 

By their oxidising action heating with copper and concen trated sulphuric acid yields brown fumes of nitrogen dioxide. 

Industrially an aqueous solution of chlorine dioxide can be prepared by passing nitrogen dioxide up a packed tower down which sodium chlorate(V) flows ... 

Like all nitrates, it is soluble in water on heating it decomposes evolving nitrogen dioxide and oxygen, but leaving the metal, and not, as is usual with other nitrates, the oxide ... 

It is also possible to use more powerful reagents to nitrate thiazoles for example, 2-methylthiazole has been nitrated using nitronium tetrafluorobo-rate and the complex nitrogen dioxide-boron tn fluoride (240). The overall yield is about 50 to 60%. 

Free radicals are species that contain unpaired electrons The octet rule notwithstand mg not all compounds have all of their electrons paired Oxygen (O2) is the most famil lar example of a compound with unpaired electrons it has two of them Compounds that have an odd number of electrons such as nitrogen dioxide (NO2) must have at least one unpaired electron... 

Ammonia, anhydrous Mercury, halogens, hypochlorites, chlorites, chlorine(I) oxide, hydrofluoric acid (anhydrous), hydrogen peroxide, chromium(VI) oxide, nitrogen dioxide, chromyl(VI) chloride, sulflnyl chloride, magnesium perchlorate, peroxodisul-fates, phosphorus pentoxide, acetaldehyde, ethylene oxide, acrolein, gold(III) chloride... 

Dimethylsulfoxide Acyl and aryl halides, boron compounds, bromomethane, nitrogen dioxide, magnesium perchlorate, periodic acid, silver difluoride, sodium hydride, sulfur trioxide... 

Indium Acetonitrile, nitrogen dioxide, mercury(II) bromide, sulfur... 

Nitrogen trichloride Ammonia, As, hydrogen sulflde, nitrogen dioxide, organic matter, ozone, phosphine, phosphorus, KCN, KOH, Se, dibutyl ether... 

Nitrogen dioxide Cyclohexane, fluorine, formaldehyde, alcohols, nitrobenzene, petroleum, toluene... 

Ozone ALkenes, aromatic compounds, bromine, diethyl ether, ethylene, HBr, HI, nitric oxide, nitrogen dioxide, rubber, stibine... 

Toluene Sulfuric plus nitric acids, nitrogen dioxide, silver perchlorate, uranium hexafluoride... 

Shooter, D. Nitrogen Dioxide and Its Determination in the Atmosphere, /. Chem. Educ. 1993, 70, A133-A140. 

Reference methods for criteria (19) and hazardous (20) poUutants estabHshed by the US EPA include sulfur dioxide [7446-09-5] by the West-Gaeke method carbon monoxide [630-08-0] by nondispersive infrared analysis ozone [10028-15-6] and nitrogen dioxide [10102-44-0] by chemiluminescence (qv) and hydrocarbons by gas chromatography coupled with flame-ionization detection. Gas chromatography coupled with a suitable detector can also be used to measure ambient concentrations of vinyl chloride monomer [75-01-4], halogenated hydrocarbons and aromatics, and polyacrylonitrile [25014-41-9] (21-22) (see Chromatography Trace and residue analysis). 

Pollutants. The problems posed by ak pollutants are very serious. Within a museum, measures can be taken to remove harmful substances as efficiently as possible by means of the installation of appropriate filter systems in the ventilation equipment. Proposed specification values for museum climate-control systems requke filtering systems having an efficiency for particulate removal in the dioctyl phthalate test of 60—80%. Systems must be able to limit both sulfur dioxide and nitrogen dioxide concentrations <10 /ig/m, and ozone to <2 /ig/m. ... 

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