Dinitrogen pentoxide
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| Names | |
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| IUPAC name
Dinitrogen pentoxide
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| Other names
Nitric anhydride
Nitronium nitrate Nitryl nitrate DNPO Anhydrous nitric acid | |
| Identifiers | |
3D model (JSmol)
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| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.030.227 |
| EC Number |
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PubChemCID
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| UNII | |
CompTox Dashboard(EPA)
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| Properties | |
| N2O5 | |
| Molar mass | 108.01 g/mol |
| Appearance | white solid |
| Density | 2.0 g/cm3[1] |
| Boiling point | 33 °C (91 °F; 306 K) sublimes[1] |
| reacts to giveHNO3 | |
| Solubility | soluble inchloroform negligible inCCl4 |
| −35.6×10−6cm3 mol−1(aq) | |
| 1.39 D | |
| Structure[2] | |
| Hexagonal,hP14 | |
| P63/mmc No. 194 | |
a= 0.54019 nm,c= 0.65268 nm
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| 2 | |
| planar,C2v(approx.D2h) N–O–N ≈ 180° | |
| Thermochemistry[3] | |
| 143.1 J K−1 mol−1(s) 95.3 J K−1 mol−1(g) | |
Std molar
entropy(S⦵298) |
178.2 J K−1 mol−1(s) 355.7 J K−1 mol−1(g) |
Std enthalpy of
formation(ΔfH⦵298) |
−43.1 kJ/mol (s) +13.3 kJ/mol (g) |
Gibbs free energy(ΔfG⦵)
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113.9 kJ/mol (s) +117.1 kJ/mol (g) |
| Hazards | |
| Occupational safety and health(OHS/OSH): | |
Main hazards
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strong oxidizer, forms strong acid in contact with water |
| NFPA 704(fire diamond) | |
| Flash point | Non-flammable |
| Related compounds | |
| Nitrous oxide Nitric oxide Dinitrogen trioxide Nitrogen dioxide Dinitrogen tetroxide | |
Related compounds
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Nitric acid |
Except where otherwise noted, data are given for materials in theirstandard state(at 25 °C [77 °F], 100 kPa).
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Dinitrogen pentoxide(also known asnitrogen pentoxideornitric anhydride) is thechemical compoundwith theformulaN2O5.It is one of the binarynitrogen oxides,a family of compounds that only containnitrogenandoxygen.It exists as colourless crystals that sublime slightly above room temperature, yielding a colorless gas.[4]
Dinitrogen pentoxide is an unstable and potentially dangerous oxidizer that once was used as areagentwhen dissolved inchloroformfornitrationsbut has largely been superseded bynitronium tetrafluoroborate(NO2BF4).
N2O5is a rare example of a compound that adopts two structures depending on the conditions. The solid is a salt,nitronium nitrate,consisting of separatenitronium cations[NO2]+andnitrate anions[NO3]−;but in the gas phase and under some other conditions it is acovalently-boundmolecule.[5]
History
[edit]N2O5was first reported byDevillein 1840, who prepared it by treatingsilver nitrate(AgNO3) withchlorine.[6][7]
Structure and physical properties
[edit]Pure solidN2O5is asalt,consisting of separated linearnitronium ionsNO+2and planar trigonalnitrateanionsNO−3.Bothnitrogencenters haveoxidation state+5. It crystallizes in the space groupD4
6h(C6/mmc) withZ= 2, with theNO−3anions in theD3hsites and theNO+2cations inD3dsites.[8]
The vapor pressureP(in atm) as a function of temperatureT(inkelvin), in the range 211 to 305 K (−62 to 32 °C), is well approximated by the formula
being about 48 torr at 0 °C, 424 torr at 25 °C, and 760 torr at 32 °C (9 °C below the melting point).[9]
In the gas phase, or when dissolved in nonpolarsolventssuch ascarbon tetrachloride,the compound exists ascovalently-bondedmoleculesO2N−O−NO2.In the gas phase, theoretical calculations for the minimum-energy configuration indicate that theO−N−Oangle in each−NO2wing is about 134° and theN−O−Nangle is about 112°. In that configuration, the two−NO2groups are rotated about 35° around the bonds to the central oxygen, away from theN−O−Nplane. The molecule thus has a propeller shape, with one axis of 180° rotational symmetry (C2)[10]
When gaseousN2O5is cooled rapidly ( "quenched" ), one can obtain themetastablemolecular form, which exothermically converts to the ionic form above −70 °C.[11]
GaseousN2O5absorbsultraviolet lightwith dissociation into thefree radicalsnitrogen dioxideNO2•andnitrogen trioxideNO3•(uncharged nitrate). The absorption spectrum has a broad band with maximum at wavelength 160nm.[12]
Preparation
[edit]A recommended laboratory synthesis entails dehydratingnitric acid(HNO3) withphosphorus(V) oxide:[11]
- P4O10+ 12 HNO3→ 4 H3PO4+ 6 N2O5
Another laboratory process is the reaction oflithium nitrateLiNO3andbromine pentafluorideBrF5,in the ratio exceeding 3:1. The reaction first formsnitryl fluorideFNO2that reacts further with the lithium nitrate:[8]
- BrF5+ 3 LiNO3→ 3 LiF + BrONO2+ O2+ 2 FNO2
- FNO2+ LiNO3→ LiF + N2O5
The compound can also be created in the gas phase by reactingnitrogen dioxideNO2orN2O4withozone:[13]
- 2 NO2+ O3→ N2O5+ O2
However, the productcatalyzesthe rapid decomposition of ozone:[13]
- 2 O3+ N2O5→ 3 O2+ N2O5
Dinitrogen pentoxide is also formed when a mixture of oxygen and nitrogen is passed through an electric discharge.[8]Another route is the reactions ofPhosphoryl chloridePOCl3ornitryl chlorideNO2Clwithsilver nitrateAgNO3[8][14]
Reactions
[edit]Dinitrogen pentoxide reacts with water (hydrolyses) to producenitric acidHNO3.Thus, dinitrogen pentoxide is theanhydrideof nitric acid:[11]
- N2O5+ H2O → 2 HNO3
Solutions of dinitrogen pentoxide in nitric acid can be seen as nitric acid with more than 100% concentration. The phase diagram of the systemH2O−N2O5shows the well-known negativeazeotropeat 60%N2O5(that is, 70%HNO3), a positive azeotrope at 85.7%N2O5(100%HNO3), and another negative one at 87.5%N2O5( "102%HNO3").[15]
The reaction withhydrogen chlorideHClalso gives nitric acid andnitryl chlorideNO2Cl:[16]
- N2O5+ HCl → HNO3+ NO2Cl
Dinitrogen pentoxide eventually decomposes at room temperature intoNO2andO2.[17][13]Decomposition is negligible if the solid is kept at 0 °C, in suitably inert containers.[8]
Dinitrogen pentoxide reacts withammoniaNH3to give several products, includingnitrous oxideN2O,ammonium nitrateNH4NO3,nitramideNH2NO2andammonium dinitramideNH4N(NO2)2,depending on reaction conditions.[18]
Decomposition of dinitrogen pentoxide at high temperatures
[edit]Dinitrogen pentoxide between high temperatures of 600 and 1,100 K (327–827 °C), is decomposed in two successive stoichiometric steps:
- N2O5→ NO2+ NO3
- 2 NO3→ 2 NO2+ O2
In the shock wave,N2O5has decomposed stoichiometrically intonitrogen dioxideandoxygen.At temperatures of 600 K and higher, nitrogen dioxide is unstable with respect tonitrogen oxideNOand oxygen. The thermal decomposition of 0.1 mM nitrogen dioxide at 1000 K is known to require about two seconds.[19]
Decomposition of dinitrogen pentoxide in carbon tetrachloride at 30 °C
[edit]Apart from the decomposition ofN2O5at high temperatures, it can also be decomposed incarbon tetrachlorideCCl4at 30 °C (303 K).[20]BothN2O5andNO2are soluble inCCl4and remain in solution while oxygen is insoluble and escapes. The volume of the oxygen formed in the reaction can be measured in a gas burette. After this step we can proceed with the decomposition, measuring the quantity ofO2that is produced over time because the only form to obtainO2is with theN2O5decomposition. The equation below refers to the decomposition ofN2O5inCCl4:
- 2 N2O5→ 4 NO2+ O2(g)
And this reaction follows the first orderrate lawthat says:
![{\displaystyle -{\frac {d[\mathrm {A} ]}{dt}}=k[\mathrm {A} ]}](https://wikimedia.org/api/rest_v1/media/math/render/svg/1ea7552714a906687c0d9bed4d10c829c4c85633)
Decomposition of nitrogen pentoxide in the presence of nitric oxide
[edit]N2O5can also be decomposed in the presence ofnitric oxideNO:
- N2O5+ NO → 3 NO2
The rate of the initial reaction between dinitrogen pentoxide and nitric oxide of the elementary unimolecular decomposition.[21]
Applications
[edit]Nitration of organic compounds
[edit]Dinitrogen pentoxide, for example as a solution inchloroform,has been used as a reagent to introduce the−NO2functionality inorganic compounds.Thisnitrationreaction is represented as follows:
- N2O5+ Ar−H → HNO3+ Ar−NO2
where Ar represents anarenemoiety.[22]The reactivity of theNO+2can be further enhanced with strong acids that generate the "super-electrophile"HNO2+2.
In this use,N2O5has been largely replaced bynitronium tetrafluoroborate[NO2]+[BF4]−.This salt retains the high reactivity ofNO+2,but it is thermally stable, decomposing at about 180 °C (intoNO2FandBF3).
Dinitrogen pentoxide is relevant to the preparation of explosives.[7][23]
Atmospheric occurrence
[edit]In theatmosphere,dinitrogen pentoxide is an important reservoir of theNOxspecies that are responsible forozone depletion:its formation provides anull cyclewith whichNOandNO2are temporarily held in an unreactive state.[24]Mixing ratiosof several parts per billion by volume have been observed in polluted regions of the nighttime troposphere.[25]Dinitrogen pentoxide has also been observed in the stratosphere[26]at similar levels, the reservoir formation having been postulated in considering the puzzling observations of a sudden drop in stratosphericNO2levels above 50 °N, the so-called 'Noxon cliff'.
Variations inN2O5reactivity inaerosolscan result in significant losses in troposphericozone,hydroxyl radicals,andNOxconcentrations.[27]Two important reactions ofN2O5in atmospheric aerosols are hydrolysis to formnitric acid[28]and reaction withhalideions, particularlyCl−,to formClNO2molecules which may serve as precursors to reactive chlorine atoms in the atmosphere.[29][30]
Hazards
[edit]N2O5is a strong oxidizer that forms explosive mixtures with organic compounds andammoniumsalts. The decomposition of dinitrogen pentoxide produces the highly toxicnitrogen dioxidegas.
References
[edit]- ^abHaynes, p. 4.76
- ^Simon, Arndt; Horakh, Jörg; Obermeyer, Axel; Borrmann, Horst (1992). "Kristalline Stickstoffoxide — Struktur von N2O3mit einer Anmerkung zur Struktur von N2O5".Angewandte Chemie(in German).104(3). Wiley: 325–327.Bibcode:1992AngCh.104..325S.doi:10.1002/ange.19921040321.
- ^Haynes, p. 5.29
- ^Connell, Peter Steele. (1979)The Photochemistry of Dinitrogen Pentoxide.Ph. D. thesis, Lawrence Berkeley National Laboratory.
- ^Angus, W.R.; Jones, R.W.; Phillips, G.O. (1949). "Existence of Nitrosyl Ions (NO+) in Dinitrogen Tetroxide and of Nitronium Ions (NO2+) in Liquid Dinitrogen Pentoxide ".Nature.164(4167): 433.Bibcode:1949Natur.164..433A.doi:10.1038/164433a0.PMID18140439.S2CID4136455.
- ^Deville, M.H. (1849)."Note sur la production de l'acide nitrique anhydre".Compt. Rend.28:257–260.
- ^abAgrawal, Jai Prakash (2010).High Energy Materials: Propellants, Explosives and Pyrotechnics.Wiley-VCH. p. 117.ISBN978-3-527-32610-5.Retrieved20 September2011.
- ^abcdeWilson, William W.; Christe, Karl O. (1987). "Dinitrogen pentoxide. New synthesis and laser Raman spectrum".Inorganic Chemistry.26(10): 1631–1633.doi:10.1021/ic00257a033.
- ^McDaniel, A. H.; Davidson, J. A.; Cantrell, C. A.; Shetter, R. E.; Calvert, J. G. (1988). "Enthalpies of formation of dinitrogen pentoxide and the nitrate free radical".The Journal of Physical Chemistry.92(14): 4172–4175.doi:10.1021/j100325a035.
- ^Parthiban, S.; Raghunandan, B.N.; Sumathi, R. (1996). "Structures, energies and vibrational frequencies of dinitrogen pentoxide".Journal of Molecular Structure: Theochem.367:111–118.doi:10.1016/S0166-1280(96)04516-2.
- ^abcHolleman, Arnold Frederik; Wiberg, Egon (2001), Wiberg, Nils (ed.),Inorganic Chemistry,translated by Eagleson, Mary; Brewer, William, San Diego/Berlin: Academic Press/De Gruyter,ISBN0-12-352651-5
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- ^abcYao, Francis; Wilson, Ivan; Johnston, Harold (1982). "Temperature-dependent ultraviolet absorption spectrum for dinitrogen pentoxide".The Journal of Physical Chemistry.86(18): 3611–3615.doi:10.1021/j100215a023.
- ^Schott, Garry; Davidson, Norman (1958). "Shock Waves in Chemical Kinetics: The Decomposition of N2O5at High Temperatures ".Journal of the American Chemical Society.80(8): 1841–1853.doi:10.1021/ja01541a019.
- ^Lloyd, L.; Wyatt, P. A. H. (1955). "The vapour pressures of nitric acid solutions. Part I. New azeotropes in the water–dinitrogen pentoxide system".J. Chem. Soc.:2248–2252.doi:10.1039/JR9550002248.
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- ^Gruenhut, N. S.; Goldfrank, M.; Cushing, M. L.; Caesar, G. V.; Caesar, P. D.; Shoemaker, C. (1950). "Nitrogen(V) Oxide (Nitrogen Pentoxide, Dinitrogen Pentoxide, Nitric Anhydride)".Inorganic Syntheses.Inorganic Syntheses. pp. 78–81.doi:10.1002/9780470132340.ch20.ISBN9780470132340.
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- ^Schott, Garry; Davidson, Norman (1958). "Shock Waves in Chemical Kinetics: The Decomposition of N2O5at High Temperatures ".Journal of the American Chemical Society.80(8): 1841–1853.doi:10.1021/ja01541a019.
- ^Jaime, R. (2008).Determinación de orden de reacción haciendo uso de integrales definidas.Universidad Nacional Autónoma de Nicaragua, Managua.
- ^Wilson, David J.; Johnston, Harold S. (1953). "Decomposition of Nitrogen Pentoxide in the Presence of Nitric Oxide. IV. Effect of Noble Gases".Journal of the American Chemical Society.75(22): 5763.doi:10.1021/ja01118a529.
- ^Bakke, Jan M.; Hegbom, Ingrid; Verne, Hans Peter; Weidlein, Johann; Schnöckel, Hansgeorg; Paulsen, Gudrun B.; Nielsen, Ruby I.; Olsen, Carl E.; Pedersen, Christian; Stidsen, Carsten E. (1994)."Dinitrogen Pentoxide--Sulfur Dioxide, a New Nitration System".Acta Chemica Scandinavica.48:181–182.doi:10.3891/acta.chem.scand.48-0181.
- ^Talawar, M. B. (2005). "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.124(1–3): 153–64.doi:10.1016/j.jhazmat.2005.04.021.PMID15979786.
- ^Finlayson-Pitts, Barbara J.; Pitts, James N. (2000).Chemistry of the upper and lower atmosphere: theory, experiments, and applications.San Diego: Academic Press.ISBN9780080529073.OCLC162128929.
- ^Wang, Haichao; Lu, Keding; Chen, Xiaorui; Zhu, Qindan; Chen, Qi; Guo, Song; Jiang, Meiqing; Li, Xin; Shang, Dongjie; Tan, Zhaofeng; Wu, Yusheng; Wu, Zhijun; Zou, Qi; Zheng, Yan; Zeng, Limin; Zhu, Tong; Hu, Min; Zhang, Yuanhang (2017). "High N2O5Concentrations Observed in Urban Beijing: Implications of a Large Nitrate Formation Pathway ".Environmental Science and Technology Letters.4(10): 416–420.doi:10.1021/acs.estlett.7b00341.
- ^Rinsland, C.P. (1989). "Stratospheric N2O5profiles at sunrise and sunset from further analysis of theATMOS/Spacelab 3solar spectra ".Journal of Geophysical Research.94:18341–18349.Bibcode:1989JGR....9418341R.doi:10.1029/JD094iD15p18341.
- ^Macintyre, H. L.; Evans, M. J. (2010-08-09)."Sensitivity of a global model to the uptake of N2O5by tropospheric aerosol ".Atmospheric Chemistry and Physics.10(15): 7409–7414.Bibcode:2010ACP....10.7409M.doi:10.5194/acp-10-7409-2010.
- ^Brown, S. S.; Dibb, J. E.; Stark, H.; Aldener, M.; Vozella, M.; Whitlow, S.; Williams, E. J.; Lerner, B. M.; Jakoubek, R. (2004-04-16)."Nighttime removal of NOxin the summer marine boundary layer ".Geophysical Research Letters.31(7): n/a.Bibcode:2004GeoRL..31.7108B.doi:10.1029/2004GL019412.
- ^Gerber, R. Benny; Finlayson-Pitts, Barbara J.; Hammerich, Audrey Dell (2015-07-15)."Mechanism for formation of atmospheric Cl atom precursors in the reaction of dinitrogen oxides with HCl/Cl−on aqueous films "(PDF).Physical Chemistry Chemical Physics.17(29): 19360–19370.Bibcode:2015PCCP...1719360H.doi:10.1039/C5CP02664D.PMID26140681.S2CID39157816.
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Cited sources
[edit]- Haynes, William M., ed. (2016).CRC Handbook of Chemistry and Physics(97th ed.).CRC Press.ISBN9781498754293.