Dinitrogen pentoxide

Dinitrogen pentoxide
Names
IUPAC name
Dinitrogen pentoxide
Other names
Nitric anhydride
Nitronium nitrate
Nitryl nitrate
DNPO
Anhydrous nitric acid
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.030.227 Edit this at Wikidata
EC Number
  • 233-264-2
UNII
  • InChI=1S/N2O5/c3-1(4)7-2(5)6 checkY
    Key: ZWWCURLKEXEFQT-UHFFFAOYSA-N checkY
  • InChI=1/N2O5/c3-1(4)7-2(5)6
    Key: ZWWCURLKEXEFQT-UHFFFAOYAN
  • gas phase: [O-][N+](=O)O[N+]([O-])=O
  • solid phase: [O]=[N+]=[O].[N+](=O)([O-])[O-]
Properties
N2O5
Molar mass 108.009 g·mol−1
Appearance white solid
Density 2.0 g/cm3
Boiling point 33 °C (91 °F; 306 K) sublimes
Reacts to form nitric acid (HNO3).
Solubility in chloroform soluble
Solubility in carbon tetrachloride slightly soluble
Vapor pressure 100 kPa (15 psi) (33.2 °C (91.8 °F))
Band gap 0.68 eV
−35.6×10−6 cm3/mol (aq)[citation needed]
1.39 D
Structure
Hexagonal, hP14
P63/mmc (No. 194)
6/mmm
a = 5.37 Å, b = 5.37 Å, c = 6.52 Å
α = 90°, β = 90°, γ = 120°
162.90 Å3
2
  • Linear at N5+ to 2·O2−
  • Trigonal planar at N5+ to 3·O2−
  • Single-bond at O2− to N5+.
Thermochemistry (solid)
143.1 J⋅mol−1⋅K−1
178.2 J⋅mol−1⋅K−1
−43.1 kJ⋅mol−1
113.9 kJ⋅mol−1
Thermochemistry (gas)
143.1 J⋅mol−1⋅K−1
355.7 J⋅mol−1⋅K−1
13.3 kJ⋅mol−1
117.1 kJ⋅mol−1
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 strong oxidizer, forms strong acid in contact with water
NFPA 704 (fire diamond)
[citation needed]
NFPA 704 four-colored diamondHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 0: Will not burn. E.g. waterInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazard W+OX: Reacts with water in an unusual or dangerous manner AND is oxidizer
4
0
2
W
OX
Related compounds
Related compounds
 Nitric acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X markN verify (what is checkYX markN ?)

Dinitrogen pentoxide (also known as nitrogen pentoxide or nitric anhydride) is the chemical compound with the formula N2O5. It is one of the binary nitrogen oxides, a family of compounds that contain only nitrogen and oxygen. It exists as colourless crystals that sublime slightly above room temperature, yielding a colorless gas.

Dinitrogen pentoxide has been used for nitrations but has largely been superseded by nitronium tetrafluoroborate (NO2BF4).

Structure

structure of gaseous N2O5

Solid N2O5 is a salt, nitronium nitrate, consisting of linear nitronium cations ([NO2]+) and planar trigonal nitrate anions ([NO3]−). The N-O distances in the cation are 115 pm (1.15 Å) and 124 pm (1.24 Å) for the anion. Gaseous N2O5 is a covalently-bound molecule. It crystallizes in the space group D4
6h (C6/mmc) with Z = 2.

In the gas phase or when dissolved in nonpolar solvents such as carbon tetrachloride, the compound exists as covalently-bonded molecules O2N−O−NO2. In the gas phase, theoretical calculations for the minimum-energy configuration indicate that the O−N−O angle in each −NO2 wing is about 134° and the N−O−N angle is about 112°. In that configuration, the two −NO2 groups are rotated about 35° around the bonds to the central oxygen, away from the N−O−N plane. The molecule thus has a propeller shape, with one axis of 180° rotational symmetry (C2).

Physical properties

The vapor pressure P (in atm) as a function of temperature T (in kelvin), in the range 211 to 305 K (−62 to 32 °C; −80 to 89 °F), is well approximated by the formula

ln P = 23.2348 - ⁠7098.2/T⁠

being about 48 Torr (6.4 kPa) at 0 °C (32 °F), 424 Torr (56.5 kPa) at 25 °C (77 °F), and 760 Torr (101 kPa) at 32 °C (90 °F), (9 °C (48 °F) below the melting point).

When gaseous N2O5 is cooled rapidly ("quenched"), one can obtain the metastable molecular form, which exothermically converts to the ionic form above −70 °C (−94 °F).

Gaseous N2O5 absorbs ultraviolet light with dissociation into the free radicals nitrogen dioxide NO•
2 and nitrogen trioxide NO•
3 (uncharged nitrate). The absorption spectrum has a broad band with maximum at wavelength 160 nm.

Preparation

N2O5 was first reported by the French chemist Henri Deville in 1840, who prepared it by treating silver nitrate (AgNO3) with chlorine.

A recommended laboratory synthesis entails dehydrating nitric acid (HNO3) with phosphorus(V) oxide (P4O10):

P4O10 + 12 HNO3 → 4 H3PO4 + 6 N2O5

Another laboratory process is the reaction of lithium nitrate (LiNO3) and bromine pentafluoride (BrF5), in the ratio exceeding 3:1. The reaction first forms nitryl fluoride (FNO2) that reacts further with the lithium nitrate:

BrF5 + 3 LiNO3 → 3 LiF + BrONO2 + O2 + 2 FNO2
FNO2 + LiNO3 → LiF + N2O5

The compound can also be created in the gas phase by reacting nitrogen dioxide (NO2) or N2O4 with ozone:

2 NO2 + O3 → N2O5 + O2

However, the product catalyzes the rapid decomposition of ozone:

2 O3 + N2O5 → 3 O2 + N2O5

Dinitrogen pentoxide is also formed when a mixture of oxygen and nitrogen is passed through an electric discharge. Another route is the reactions of phosphoryl chloride (POCl3) or nitryl chloride (NO2Cl) with silver nitrate (AgNO3).

Reactions

Sublimed dinitrogen pentoxide crystals

Dinitrogen pentoxide reacts with water (hydrolyses) to produce nitric acid (HNO3). Thus, dinitrogen pentoxide is an acidic oxide, the anhydride of nitric acid:

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 system H2O−N2O5 shows the well-known negative azeotrope at 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").

The reaction with hydrogen chloride (HCl) also gives nitric acid and nitryl chloride (NO2Cl):

N2O5 + HCl → HNO3 + NO2Cl

Dinitrogen pentoxide reacts with ammonia (NH3) to give several products, including nitrous oxide (N2O), ammonium nitrate (NH4NO3), nitramide (NH2NO2), and ammonium dinitramide (NH4N(NO2)2), depending on reaction conditions.

Thermal decomposition

Decomposition is negligible if the solid is kept at 0 °C (32 °F). It decomposes at room temperature into nitrogen dioxide (NO2) and O2:

N2O5 → 2 NO2 + 0.5 O2

Its solutions in carbon tetrachloride (CCl4) decompose at 30 °C (86 °F).[verification needed] Both N2O5 and NO2 are soluble in CCl4 and remain in solution while oxygen is insoluble and escapes. The volume of the oxygen allows determination of the reaction kinetics:

2 N2O5 → 4 NO2 + O2(g)

In the presence of nitric oxide (NO), the decomposition proceeds as follows:

N2O5 + NO → 3 NO2

Applications

Nitration of organic compounds

Dinitrogen pentoxide, for example as a solution in chloroform (CHCl3), has been used as a reagent to introduce the −NO2 functionality in organic compounds. This nitration reaction is represented as follows:

N2O5 + Ar−H → HNO3 + Ar−NO2

Where Ar represents an arene moiety. The reactivity of the NO+2 can be further enhanced with strong acids that generate the superelectrophile HNO2+2.

In this use, N2O5 has been largely replaced by nitronium tetrafluoroborate ([NO2]+[BF4]−). This salt retains the high reactivity of NO+2, but it is thermally stable, decomposing at about 180 °C (356 °F) (into nitryl fluoride (NO2F) and boron trifluoride (BF3)).[citation needed]

Dinitrogen pentoxide is relevant to the preparation of explosives.

Atmospheric occurrence

In Earth's atmosphere, dinitrogen pentoxide is an important reservoir of the NOx species that are responsible for ozone depletion: its formation provides a null cycle with which NO and NO2 are temporarily held in an unreactive state. Mixing ratios of several parts per billion by volume have been observed in polluted regions of the nighttime troposphere. Dinitrogen pentoxide has also been observed in the stratosphere at similar levels, the reservoir formation having been postulated in considering the puzzling observations of a sudden drop in stratospheric NO2 levels above 50° N, the so-called 'Noxon cliff'.

Variations in N2O5 reactivity in aerosols can result in significant losses in tropospheric ozone, hydroxyl radicals, and NOx concentrations. Two important reactions of N2O5 in atmospheric aerosols are hydrolysis to form nitric acid and reaction with halide ions, particularly Cl−, to form nitryl chloride (ClNO2) molecules which may serve as precursors to reactive chlorine atoms in the atmosphere.

Hazards

N2O5 is a strong oxidizer that forms explosive mixtures with organic compounds and ammonium salts. Dinitrogen pentoxide can degrade to the highly toxic nitrogen dioxide gas.[citation needed]

References

  1. 1 2 3 Haynes, William M., ed. (2016). CRC Handbook of Chemistry and Physics (97th ed.). Boca Raton, Florida: CRC Press. pp. 4–76, 5–29, 6–117. ISBN 9781498754293.
  2. 1 2 "Materials Data on N2O5". next-gen.materialsproject.org. Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA: LBNL Materials Project. 15 July 2020. doi:10.17188/1262043. Retrieved 27 August 2026.
  3. ↑ Connell, Peter Steele. (1979) The Photochemistry of Dinitrogen Pentoxide. Ph. D. thesis, Lawrence Berkeley National Laboratory.
  4. ↑ Grison, E.; Eriks, K.; De Vries, J. L. (1950). "Structure cristalline de l'anhydride azotique, N2O5". Acta Crystallographica. 3 (4): 290–294. doi:10.1107/S0365110X50000744.
  5. ↑ 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. PMID 18140439. S2CID 4136455.
  6. 1 2 3 4 5 Wilson, William W.; Christe, Karl O. (1987). "Dinitrogen pentoxide. New synthesis and laser Raman spectrum". Inorganic Chemistry. 26 (10): 1631–1633. doi:10.1021/ic00257a033.
  7. ↑ 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.
  8. ↑ 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.
  9. 1 2 3 Holleman, Arnold Frederik; Wiberg, Egon (2001), Wiberg, Nils (ed.), Inorganic Chemistry, translated by Eagleson, Mary; Brewer, William, San Diego/Berlin: Academic Press/De Gruyter, ISBN 0-12-352651-5[pages needed]
  10. ↑ Osborne, Bruce A.; Marston, George; Kaminski, L.; Jones, N.C; Gingell, J.M; Mason, Nigel; Walker, Isobel C.; Delwiche, J.; Hubin-Franskin, M.-J. (2000). "Vacuum ultraviolet spectrum of dinitrogen pentoxide". Journal of Quantitative Spectroscopy and Radiative Transfer. 64 (1): 67–74. Bibcode:2000JQSRT..64...67O. doi:10.1016/S0022-4073(99)00104-1.
  11. ↑ Deville, M.H. (1849). "Note sur la production de l'acide nitrique anhydre". Compt. Rend. (in French). 28: 257–260.
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  14. ↑ Schott, Garry; Davidson, Norman (1958). "Shock Waves in Chemical Kinetics: The Decomposition of N2O5 at High Temperatures". Journal of the American Chemical Society. 80 (8): 1841–1853. Bibcode:1958JAChS..80.1841S. doi:10.1021/ja01541a019.
  15. ↑ 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.
  16. ↑ Wilkins, Robert A.; Hisatsune, I. C. (1976). "The Reaction of Dinitrogen Pentoxide with Hydrogen Chloride". Industrial & Engineering Chemistry Fundamentals. 15 (4): 246–248. doi:10.1021/i160060a003.
  17. ↑ Frenck, C.; Weisweiler, W. (2002). "Modeling the Reactions Between Ammonia and Dinitrogen Pentoxide to Synthesize Ammonium Dinitramide (ADN)". Chemical Engineering & Technology. 25 (2): 123. doi:10.1002/1521-4125(200202)25:2<123::AID-CEAT123>3.0.CO;2-W.
  18. ↑ Gruenhut, N. S.; Goldfrank, M.; Cushing, M. L.; Caesar, G. V.; Caesar, P. D.; Shoemaker, C. "Nitrogen(V) Oxide (Nitrogen Pentoxide, Dinitrogen Pentoxide, Nitric Anhydride)". Inorganic Syntheses. pp. 78–81. doi:10.1002/9780470132340.ch20. ISBN 9780470132340.
  19. ↑ Schott, Garry; Davidson, Norman (1958). "Shock Waves in Chemical Kinetics: The Decomposition of N2O5 at High Temperatures". Journal of the American Chemical Society. 80 (8): 1841–1853. Bibcode:1958JAChS..80.1841S. doi:10.1021/ja01541a019.
  20. ↑ Jaime, R. (2008). Determinación de orden de reacción haciendo uso de integrales definidas. Universidad Nacional Autónoma de Nicaragua, Managua.
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  22. ↑ 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.
  23. ↑ 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. Bibcode:2005JHzM..124..153T. doi:10.1016/j.jhazmat.2005.04.021. PMID 15979786.
  24. ↑ Finlayson-Pitts, Barbara J.; Pitts, James N. (2000). Chemistry of the upper and lower atmosphere: theory, experiments, and applications. San Diego: Academic Press. ISBN 9780080529073. OCLC 162128929.
  25. ↑ 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 N2O5 Concentrations Observed in Urban Beijing: Implications of a Large Nitrate Formation Pathway". Environmental Science and Technology Letters. 4 (10): 416–420. Bibcode:2017EnSTL...4..416W. doi:10.1021/acs.estlett.7b00341.
  26. ↑ Rinsland, C.P. (1989). "Stratospheric N2O5 profiles at sunrise and sunset from further analysis of the ATMOS/Spacelab 3 solar spectra". Journal of Geophysical Research. 94: 18341–18349. Bibcode:1989JGR....9418341R. doi:10.1029/JD094iD15p18341.
  27. ↑ Macintyre, H. L.; Evans, M. J. (2010-08-09). "Sensitivity of a global model to the uptake of N2O5 by tropospheric aerosol". Atmospheric Chemistry and Physics. 10 (15): 7409–7414. Bibcode:2010ACP....10.7409M. doi:10.5194/acp-10-7409-2010.
  28. ↑ 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 NOx in the summer marine boundary layer". Geophysical Research Letters. 31 (7): n/a. Bibcode:2004GeoRL..31.7108B. doi:10.1029/2004GL019412.
  29. ↑ 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. PMID 26140681. S2CID 39157816.
  30. ↑ Kelleher, Patrick J.; Menges, Fabian S.; DePalma, Joseph W.; Denton, Joanna K.; Johnson, Mark A.; Weddle, Gary H.; Hirshberg, Barak; Gerber, R. Benny (2017-09-18). "Trapping and Structural Characterization of the XNO2·NO3− (X=Cl, Br, I) Exit Channel Complexes in the Water-Mediated X− + N2O5 Reactions with Cryogenic Vibrational Spectroscopy". The Journal of Physical Chemistry Letters. 8 (19): 4710–4715. doi:10.1021/acs.jpclett.7b02120. PMID 28898581.