dinitrogen pentoxide

{{chem2|N2O5}} was first reported by the French chemist Henri Deville in 1840, who prepared it by treating silver nitrate ({{chem2|AgNO3}}) with chlorine.{{cite journal|author=Deville, M.H. |journal= Compt. Rend. |volume=28 |year=1849|title=Note sur la production de l'acide nitrique anhydre|url=https://archive.org/details/comptesrendusheb28acad/page/257|pages=257–260}}{{cite book|author=Agrawal, Jai Prakash |title=High Energy Materials: Propellants, Explosives and Pyrotechnics|url=https://books.google.com/books?id=rqZROysoS7QC&pg=PA117|access-date=20 September 2011|date=2010|publisher=Wiley-VCH|isbn=978-3-527-32610-5|page=117}}

Pure solid {{chem2|N2O5}} is a salt, consisting of separated linear nitronium ions {{chem2|NO2+}} and planar trigonal nitrate anions {{chem2|NO3-}}. Both nitrogen centers have oxidation state +5. It crystallizes in the space group D{{su|p=4|b=6h}} (C6/mmc) with Z = 2, with the {{chem2|NO3-}} anions in the D_3h sites and the {{chem2|NO2+}} cations in D_3d sites.

The vapor pressure P (in atm) as a function of temperature T (in kelvin), in the range {{cvt|211|to|305|K|C}}, is well approximated by the formula

:$\backslash ln\; P\; =\; 23.2348\; -\; \backslash frac\{7098.2\}\{T\}$

being about 48 torr at 0 °C, 424 torr at 25 °C, and 760 torr at 32 °C (9 °C below the melting point).{{cite journal|doi=10.1021/j100325a035|title=Enthalpies of formation of dinitrogen pentoxide and the nitrate free radical |year=1988 |last1=McDaniel |first1=A. H. |last2=Davidson |first2=J. A. |last3=Cantrell |first3=C. A. |last4=Shetter |first4=R. E. |last5=Calvert |first5=J. G. |journal=The Journal of Physical Chemistry |volume=92 |issue=14 |pages=4172–4175 }}

In the gas phase, or when dissolved in nonpolar solvents such as carbon tetrachloride, the compound exists as covalently-bonded molecules {{chem2|O2N\sO\sNO2}}. In the gas phase, theoretical calculations for the minimum-energy configuration indicate that the {{chem2|O\sN\sO}} angle in each {{chem2|\sNO2}} wing is about 134° and the {{chem2|N\sO\sN}} angle is about 112°. In that configuration, the two {{chem2|\sNO2}} groups are rotated about 35° around the bonds to the central oxygen, away from the {{chem2|N\sO\sN}} plane. The molecule thus has a propeller shape, with one axis of 180° rotational symmetry (C₂) {{cite journal|doi=10.1016/S0166-1280(96)04516-2|title=Structures, energies and vibrational frequencies of dinitrogen pentoxide |year=1996 |last1=Parthiban |first1=S. |last2=Raghunandan |first2=B.N. |last3=Sumathi |first3=R. |journal=Journal of Molecular Structure: Theochem |volume=367 |pages=111–118 }}

When gaseous {{chem2|N2O5}} is cooled rapidly ("quenched"), one can obtain the metastable molecular form, which exothermically converts to the ionic form above −70 °C.

Gaseous {{chem2|N2O5}} absorbs ultraviolet light with dissociation into the free radicals nitrogen dioxide {{chem2|NO2^{•}|}} and nitrogen trioxide {{chem2|NO3^{•}|}} (uncharged nitrate). The absorption spectrum has a broad band with maximum at wavelength 160 nm.{{cite journal|doi=10.1016/S0022-4073(99)00104-1|title=Vacuum ultraviolet spectrum of dinitrogen pentoxide |year=2000 |last1=Osborne |first1=Bruce A. |last2=Marston |first2=George |last3=Kaminski |first3=L. |last4=Jones |first4=N.C |last5=Gingell |first5=J.M |last6=Mason |first6=Nigel |last7=Walker |first7=Isobel C. |last8=Delwiche |first8=J. |last9=Hubin-Franskin |first9=M.-J. |journal=Journal of Quantitative Spectroscopy and Radiative Transfer |volume=64 |issue=1 |pages=67–74 |bibcode=2000JQSRT..64...67O }}

A recommended laboratory synthesis entails dehydrating nitric acid ({{chem2|HNO3}}) with phosphorus(V) oxide:{{Holleman&Wiberg}}

:{{chem2|P4O10 + 12 HNO3 → 4 H3PO4 + 6 N2O5}}

Another laboratory process is the reaction of lithium nitrate {{chem2|LiNO3}} and bromine pentafluoride {{chem2|BrF5}}, in the ratio exceeding 3:1. The reaction first forms nitryl fluoride {{chem2|FNO2}} that reacts further with the lithium nitrate:

: {{chem2|BrF5 + 3 LiNO3 → 3 LiF + BrONO2 + O2 + 2 FNO2}}

: {{chem2|FNO2 + LiNO3 → LiF + N2O5}}

The compound can also be created in the gas phase by reacting nitrogen dioxide {{chem2|NO2}} or {{chem2|N2O4}} with ozone:{{cite journal|doi=10.1021/j100215a023|title=Temperature-dependent ultraviolet absorption spectrum for dinitrogen pentoxide |year=1982 |last1=Yao |first1=Francis |last2=Wilson |first2=Ivan |last3=Johnston |first3=Harold |journal=The Journal of Physical Chemistry |volume=86 |issue=18 |pages=3611–3615 }}

: {{chem2|2 NO2 + O3 → N2O5 + O2}}

However, the product catalyzes the rapid decomposition of ozone:

: {{chem2|2 O3 + N2O5 → 3 O2 + N2O5}}

Dinitrogen pentoxide is also formed when a mixture of oxygen and nitrogen is passed through an electric

discharge.{{cite journal|doi=10.1021/ic00257a033|title=Dinitrogen pentoxide. New synthesis and laser Raman spectrum |year=1987 |last1=Wilson |first1=William W. |last2=Christe |first2=Karl O. |journal=Inorganic Chemistry |volume=26 |issue=10 |pages=1631–1633 }} Another route is the reactions of Phosphoryl chloride {{chem2|POCl3}} or nitryl chloride {{chem2|NO2Cl}} with silver nitrate {{chem2|AgNO3}}{{cite journal|doi=10.1021/ja01541a019|title=Shock Waves in Chemical Kinetics: The Decomposition of N₂O₅ at High Temperatures|year=1958 |last1=Schott |first1=Garry |last2=Davidson |first2=Norman |journal=Journal of the American Chemical Society |volume=80 |issue=8 |pages=1841–1853 |bibcode=1958JAChS..80.1841S }}

Dinitrogen pentoxide reacts with water (hydrolyses) to produce nitric acid {{chem2|HNO3}}. Thus, dinitrogen pentoxide is the anhydride of nitric acid:

:{{chem2|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 {{chem2|H2O}}−{{chem2|N2O5}} shows the well-known negative azeotrope at 60% {{chem2|N2O5}} (that is, 70% {{chem2|HNO3}}), a positive azeotrope at 85.7% {{chem2|N2O5}} (100% {{chem2|HNO3}}), and another negative one at 87.5% {{chem2|N2O5}} ("102% {{chem2|HNO3}}").{{cite journal|doi=10.1039/JR9550002248|title=The vapour pressures of nitric acid solutions. Part I. New azeotropes in the water–dinitrogen pentoxide system |year=1955 |last1=Lloyd |first1=L. |last2=Wyatt |first2=P. A. H. |journal=J. Chem. Soc. |pages=2248–2252 }}

The reaction with hydrogen chloride {{chem2|HCl}} also gives nitric acid and nitryl chloride {{chem2|NO2Cl}}:{{cite journal|doi=10.1021/i160060a003|title=The Reaction of Dinitrogen Pentoxide with Hydrogen Chloride |year=1976 |last1=Wilkins |first1=Robert A. |last2=Hisatsune |first2=I. C. |journal=Industrial & Engineering Chemistry Fundamentals |volume=15 |issue=4 |pages=246–248 }}

: {{chem2|N2O5 + HCl → HNO3 + NO2Cl}}

Dinitrogen pentoxide eventually decomposes at room temperature into nitrogen dioxide and oxygen.{{cite book | last1=Gruenhut | first1=N. S. | last2=Goldfrank | first2=M. | last3=Cushing | first3=M. L. | last4=Caesar | first4=G. V. | last5=Caesar | first5=P. D. | last6=Shoemaker | first6=C. | title=Inorganic Syntheses | chapter=Nitrogen(V) Oxide (Nitrogen Pentoxide, Dinitrogen Pentoxide, Nitric Anhydride)| date=1950| doi=10.1002/9780470132340.ch20 | pages=78–81| isbn=9780470132340 }} Decomposition is negligible if the solid is kept at 0 °C, in suitably inert containers.

Dinitrogen pentoxide reacts with ammonia {{chem2|NH3}} to give several products, including nitrous oxide {{chem2|N2O}}, ammonium nitrate {{chem2|NH4NO3}}, nitramide {{chem2|NH2NO2}} and ammonium dinitramide {{chem2|NH4N(NO2)2}}, depending on reaction conditions.{{cite journal|doi=10.1002/1521-4125(200202)25:2<123::AID-CEAT123>3.0.CO;2-W|title=Modeling the Reactions Between Ammonia and Dinitrogen Pentoxide to Synthesize Ammonium Dinitramide (ADN) |year=2002 |last1=Frenck |first1=C. |last2=Weisweiler |first2=W. |journal=Chemical Engineering & Technology |volume=25 |issue=2 |page=123 }}

Dinitrogen pentoxide between high temperatures of {{cvt|600|and(-)|1100|K|C}}, is decomposed in two successive stoichiometric steps:

: {{chem2|N2O5 → NO2 + NO3}}

: {{chem2|2 NO3 → 2 NO2 + O2}}

In the shock wave, {{chem2|N2O5}} has decomposed stoichiometrically into nitrogen dioxide and oxygen. At temperatures of 600 K and higher, nitrogen dioxide is unstable with respect to nitrogen oxide {{chem|NO}} and oxygen. The thermal decomposition of 0.1 mM nitrogen dioxide at 1000 K is known to require about two seconds.{{cite journal|doi=10.1021/ja01541a019|title=Shock Waves in Chemical Kinetics: The Decomposition of N₂O₅ at High Temperatures|year=1958 |last1=Schott |first1=Garry |last2=Davidson |first2=Norman |journal=Journal of the American Chemical Society |volume=80 |issue=8 |pages=1841–1853 |bibcode=1958JAChS..80.1841S }}

Apart from the decomposition of {{chem2|N2O5}} at high temperatures, it can also be decomposed in carbon tetrachloride {{chem2|CCl4}} at {{cvt|30|C|K}}.Jaime, R. (2008). [https://www.researchgate.net/publication/343920548 Determinación de orden de reacción haciendo uso de integrales definidas]. Universidad Nacional Autónoma de Nicaragua, Managua. Both {{chem2|N2O5}} and {{chem2|NO2}} are soluble in {{chem2|CCl4}} and 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 of {{chem2|O2}} that is produced over time because the only form to obtain {{chem2|O2}} is with the {{chem2|N2O5}} decomposition. The equation below refers to the decomposition of {{chem2|N2O5}} in {{chem2|CCl4}}:

: {{chem2|2 N2O5 → 4 NO2 + O2(g)}}

And this reaction follows the first order rate law that says:

:$-\backslash frac\{d[\backslash mathrm\{A\}]\}\{dt\}\; =\; k\; [\backslash mathrm\{A\}]$

{{chem2|N2O5}} can also be decomposed in the presence of nitric oxide {{chem2|NO}}:

: {{chem2|N2O5 + NO → 3 NO2}}

The rate of the initial reaction between dinitrogen pentoxide and nitric oxide of the elementary unimolecular decomposition.{{cite journal |title=Decomposition of Nitrogen Pentoxide in the Presence of Nitric Oxide. IV. Effect of Noble Gases|journal=Journal of the American Chemical Society|year=1953 |volume=75 |issue=22 |page=5763 |doi=10.1021/ja01118a529 |last1=Wilson |first1=David J. |last2=Johnston |first2=Harold S. |bibcode=1953JAChS..75.5763W }}

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

:{{chem2|N2O5 + Ar\sH → HNO3 + Ar\sNO2}}

where Ar represents an arene moiety.{{cite journal|doi=10.3891/acta.chem.scand.48-0181|title=Dinitrogen Pentoxide--Sulfur Dioxide, a New Nitration System |year=1994 |last1=Bakke |first1=Jan M. |last2=Hegbom |first2=Ingrid |last3=Verne |first3=Hans Peter |last4=Weidlein |first4=Johann |last5=Schnöckel |first5=Hansgeorg |last6=Paulsen |first6=Gudrun B. |last7=Nielsen |first7=Ruby I. |last8=Olsen |first8=Carl E. |last9=Pedersen |first9=Christian |last10=Stidsen |first10=Carsten E. |journal=Acta Chemica Scandinavica |volume=48 |pages=181–182 |doi-access=free }} The reactivity of the {{chem2|NO2+}} can be further enhanced with strong acids that generate the "super-electrophile" {{chem2|HNO2(2+)}}.

In this use, {{chem2|N2O5}} has been largely replaced by nitronium tetrafluoroborate {{chem2|[NO2]+[BF4]-}}. This salt retains the high reactivity of {{chem2|NO2+}}, but it is thermally stable, decomposing at about 180 °C (into nitryl fluoride and boron trifluoride).

Dinitrogen pentoxide is relevant to the preparation of explosives.{{cite journal|author=Talawar, M. B.|title=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=Journal of Hazardous Materials|year= 2005| volume =124|issue=1–3| pages =153–64|doi=10.1016/j.jhazmat.2005.04.021|pmid=15979786|bibcode=2005JHzM..124..153T }}

In the atmosphere, dinitrogen pentoxide is an important reservoir of the {{chem2|NO_{x}|}} species that are responsible for ozone depletion: its formation provides a null cycle with which {{chem2|NO}} and {{chem2|NO2}} are temporarily held in an unreactive state.{{Cite book|title=Chemistry of the upper and lower atmosphere : theory, experiments, and applications|last1=Finlayson-Pitts|first1=Barbara J.|last2=Pitts|first2=James N.|date=2000|publisher=Academic Press|isbn=9780080529073|location=San Diego|oclc=162128929}} Mixing ratios of several parts per billion by volume have been observed in polluted regions of the nighttime troposphere.{{cite journal|title=High N₂O₅ Concentrations Observed in Urban Beijing: Implications of a Large Nitrate Formation Pathway|journal=Environmental Science and Technology Letters|volume=4|issue=10|pages=416–420|year= 2017|doi=10.1021/acs.estlett.7b00341|last1=Wang |first1=Haichao |last2=Lu |first2=Keding |last3=Chen |first3=Xiaorui |last4=Zhu |first4=Qindan |last5=Chen |first5=Qi |last6=Guo |first6=Song |last7=Jiang |first7=Meiqing |last8=Li |first8=Xin |last9=Shang |first9=Dongjie |last10=Tan |first10=Zhaofeng |last11=Wu |first11=Yusheng |last12=Wu |first12=Zhijun |last13=Zou |first13=Qi |last14=Zheng |first14=Yan |last15=Zeng |first15=Limin |last16=Zhu |first16=Tong |last17=Hu |first17=Min |last18=Zhang |first18=Yuanhang |bibcode=2017EnSTL...4..416W }} Dinitrogen pentoxide has also been observed in the stratosphere{{cite journal|author=Rinsland, C.P. |title=Stratospheric N₂O₅ profiles at sunrise and sunset from further analysis of the ATMOS/Spacelab 3 solar spectra|journal=Journal of Geophysical Research|year= 1989|volume =94| pages =18341–18349|doi=10.1029/JD094iD15p18341|bibcode=1989JGR....9418341R}} at similar levels, the reservoir formation having been postulated in considering the puzzling observations of a sudden drop in stratospheric {{chem2|NO2}} levels above 50 °N, the so-called 'Noxon cliff'.

Variations in {{chem2|N2O5}} reactivity in aerosols can result in significant losses in tropospheric ozone, hydroxyl radicals, and {{chem2|NO_{x}|}} concentrations.{{Cite journal|last1=Macintyre|first1=H. L.|last2=Evans|first2=M. J.|date=2010-08-09|title=Sensitivity of a global model to the uptake of N₂O₅ by tropospheric aerosol|journal=Atmospheric Chemistry and Physics|volume=10|issue=15|pages=7409–7414|doi=10.5194/acp-10-7409-2010|bibcode=2010ACP....10.7409M|doi-access=free}} Two important reactions of {{chem2|N2O5}} in atmospheric aerosols are hydrolysis to form nitric acid{{Cite journal|last1=Brown|first1=S. S.|last2=Dibb|first2=J. E.|last3=Stark|first3=H.|last4=Aldener|first4=M.|last5=Vozella|first5=M.|last6=Whitlow|first6=S.|last7=Williams|first7=E. J.|last8=Lerner|first8=B. M.|last9=Jakoubek|first9=R.|date=2004-04-16|title=Nighttime removal of NO_x in the summer marine boundary layer|journal=Geophysical Research Letters|language=en|volume=31|issue=7|pages=n/a|doi=10.1029/2004GL019412|bibcode=2004GeoRL..31.7108B|doi-access=free}} and reaction with halide ions, particularly chloride, to form ClNO2 molecules which may serve as precursors to reactive chlorine atoms in the atmosphere.{{Cite journal|last1=Gerber|first1=R. Benny|last2=Finlayson-Pitts|first2=Barbara J.|last3=Hammerich|first3=Audrey Dell|date=2015-07-15|title=Mechanism for formation of atmospheric Cl atom precursors in the reaction of dinitrogen oxides with HCl/Cl⁻ on aqueous films|journal=Physical Chemistry Chemical Physics|language=en|volume=17|issue=29|pages=19360–19370|doi=10.1039/C5CP02664D|pmid=26140681|bibcode=2015PCCP...1719360H|s2cid=39157816 |url=https://escholarship.org/content/qt3087m4xv/qt3087m4xv.pdf?t=oubfuu}}{{Cite journal|last1=Kelleher|first1=Patrick J.|last2=Menges|first2=Fabian S.|last3=DePalma|first3=Joseph W.|last4=Denton|first4=Joanna K.|last5=Johnson|first5=Mark A.|last6=Weddle|first6=Gary H.|last7=Hirshberg|first7=Barak|last8=Gerber|first8=R. Benny|date=2017-09-18|title=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|journal=The Journal of Physical Chemistry Letters|volume=8|issue=19|pages=4710–4715|doi=10.1021/acs.jpclett.7b02120|pmid=28898581}}

{{chem2|N2O5}} 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.

{{reflist}}

• {{cite book | editor= Haynes, William M. | date = 2016| title = CRC Handbook of Chemistry and Physics | edition = 97th | publisher = CRC Press | isbn = 9781498754293}}

{{Oxides}}

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{{DEFAULTSORT:Dinitrogen Pentoxide}}

Category:Nitrogen oxides

Category:Acid anhydrides

Category:Acidic oxides

Category:Nitrates

Category:Nitronium compounds