Dinitrogen pentoxide 584602 209900830 2008-05-03T13:40:14Z BOTarate 5870361 robot Modifying: [[es:Óxido de nitrógeno (V)]] {{Chembox new | Name = Dinitrogen pentoxide | ImageFile = Dinitrogen-pentoxide-3D-balls.png | ImageSize = 200px | ImageName = Dinitrogen pentoxide | OtherNames = dinitrogen pentoxide<br />dnpo | Section1 = {{Chembox Identifiers | CASNo = 10102-03-1 | RTECS = }} | Section2 = {{Chembox Properties | Formula = N<sub>2</sub>O<sub>5</sub> | MolarMass = 108.01 g mol<sup>-1</sup> | Appearance = white solid | Density = 2.05 g cm<sup>-3</sup>, solid | Solubility = decomp. to HNO<sub>3</sub> | MeltingPt = 41 °C (under pressure<br /> to suppress sublimation) | BoilingPt = decomposes }} | Section3 = {{Chembox Structure | Coordination = linear at N<sub>2</sub>O and planar at NO<sub>3</sub> }} | Section7 = {{Chembox Hazards | ExternalMSDS = [[Dinitrogen pentoxide chemdata supplement#Material Safety Data Sheet|External MSDS]] | MainHazards = strong oxidizer, forms strong<br /> acid in contact with water }} }} '''Dinitrogen pentoxide''' is the [[chemical compound]] with the [[chemical formula|formula]] N<sub>2</sub>O<sub>5</sub>. Also known as nitrogen pentoxide, N<sub>2</sub>O<sub>5</sub> is one of the binary [[nitrogen]] [[oxygen|oxide]]s a family of compounds that only contain nitrogen and oxygen. It is an unstable and potentially dangerous oxidizer that once was used as a [[reagent]] for [[nitration]]s but has largely been superseded by NO<sub>2</sub>BF<sub>4</sub> ([[nitronium tetrafluoroborate]]). N<sub>2</sub>O<sub>5</sub> is a rare example of a compound that adopts two structures depending on the conditions: most commonly it is a salt, but under some conditions it is a nonpolar molecule: :N<sub>2</sub>O<sub>5</sub> {{unicode|⇌}} [NO<sub>2</sub><sup>+</sup>][NO<sub>3</sub><sup>−</sup>] ==Syntheses and properties== N<sub>2</sub>O<sub>5</sub> was first reported by Deville in 1840, who prepared it by treating AgNO<sub>3</sub> with [[chlorine|Cl<sub>2</sub>]]. A recommended laboratory synthesis entails dehydrating [[nitric acid]] (HNO<sub>3</sub>) with [[Phosphorus pentoxide|phosphorus(V) oxide]]:<ref name=Holl>Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.</ref> :P<sub>4</sub>O<sub>10</sub> + 12 HNO<sub>3</sub> &rarr; 4 H<sub>3</sub>PO<sub>4</sub> + 6 N<sub>2</sub>O<sub>5</sub> In the reverse process, N<sub>2</sub>O<sub>5</sub> reacts with water ([[hydrolysis|hydrolyses]]) to produce nitric acid. Thus, nitrogen pentoxide is the [[anhydride]] of nitric acid: :N<sub>2</sub>O<sub>5</sub> + H<sub>2</sub>O &rarr; 2 HNO<sub>3</sub> N<sub>2</sub>O<sub>5</sub> exists as colourless crystals that sublime slightly above room temperature. The salt eventually decomposes at room temperature into [[nitrogen dioxide|NO<sub>2</sub>]] and [[oxygen|O<sub>2</sub>]]. <ref>"Nitrogen(V) Oxide" in "Inorganic Syntheses" McGraw-Hill, vol. III, pages 78-81, 1950.</ref> ==Structure== Solid N<sub>2</sub>O<sub>5</sub></sub> is a [[salt]], consisting of separated anions and cations. The cation is the linear [[nitronium]] ion NO<sub>2</sub><sup>+</sup> and the anion is planar NO<sub>3</sub><sup>&minus;</sup> ions. Thus, the solid could be called [[nitronium]] [[nitrate]]. Both [[nitrogen]] centers have oxidation states V. The intact molecule O<sub>2</sub>N-O-NO<sub>2</sub> exists in the gas phase (obtained by subliming N<sub>2</sub>O<sub>5</sub></sub>) and when the solid is extracted into nonpolar [[solvent]]s such as [[carbon tetrachloride|CCl<sub>4</sub>]]. In the gas phase, the O-N-O angle is 133° and the N-O-N angle is 114°. When gaseous N<sub>2</sub>O<sub>5</sub></sub> is cooled rapidly ("quenched"), one can obtain the metastable molecular form, which exothermically converts to the ionic form above -70 °C.<ref name=Holl/> ::N<sub>2</sub>O<sub>5</sub> [[Lewis Structure]]: ::[[Image:N2O5.svg|Structure of the (rare) molecular form of dinitrogen pentoxide]] ==Reactions and applications== Dinitrogen pentoxide, for example as a solution in [[chloroform]], has been used as a reagent to introduce the NO<sub>2</sub> functionality. This [[nitration]] reaction is represented as follows: ::N<sub>2</sub>O<sub>5</sub> + [[arene|Ar]]-H &rarr; HNO<sub>3</sub> + Ar-NO<sub>2</sub> N<sub>2</sub>O<sub>5</sub> is of interest for the preparation of explosives.<ref>Talawar, M. B.; Sivabalan, R.; Polke, B. G.; Nair, U. R.; Gore, G. M.; Asthana, S. N. "Establishment of Process Technology for the Manufacture of Dinitrogen Pentoxide and its Utility for the Synthesis of Most Powerful Explosive of Today--CL-20", Journal of Hazardous Materials, 2005, volume 124, pages 153-64.</ref> ==NO<sub>2</sub>BF<sub>4</sub>== Replacement of the NO<sub>3</sub><sup>&minus;</sup> portion of N<sub>2</sub>O<sub>5</sub> with BF<sub>4</sub><sup>&minus;</sup> gives NO<sub>2</sub>BF<sub>4</sub> (CAS#13826-86-3). This salt retains the high reactivity of NO<sub>2</sub><sup>+</sup>, but it is thermally stable, decomposing at ca. 180°C (into NO<sub>2</sub>F and BF<sub>3</sub>). NO<sub>2</sub>BF<sub>4</sub> has been used to nitrate a variety of organic compounds, especially arenes and heterocycles. Interestingly, the reactivity of the NO<sub>2</sub><sup>+</sup> can be further enhanced with strong acids that generate the "super-electrophile" HNO<sub>2</sub><sup>2+</sup>. ==Hazards== N<sub>2</sub>O<sub>5</sub> is a strong oxidizer that forms explosive mixtures with organic compounds and [[ammonium]] salts. The decomposition of dinitrogen pentoxide produces the highly toxic [[nitrogen dioxide]] gas. ==References== <references/> [[Category:Oxides]] [[Category:Nitrogen compounds]] [[Category:Acidic oxides]] [[cs:Oxid dusičný]] [[da:Dinitrogenpentoxid]] [[de:Distickstoffpentoxid]] [[es:Óxido de nitrógeno (V)]] [[it:Pentossido di diazoto]] [[ja:五酸化二窒素]] [[pl:Tlenek azotu(V)]] [[ru:Оксид азота(V)]] [[zh:五氧化二氮]]