Peroxyacetyl nitrate

Peroxyacetyl nitrate is a peroxyacyl nitrate. It is a secondary pollutant present in photochemical smog.^[1] It is thermally unstable and decomposes into peroxyethanoyl radicals and nitrogen dioxide gas.^[2] It is a lachrymatory substance, meaning that it irritates the lungs and eyes.^[3]

Peroxyacetyl nitrate

Names
Preferred IUPAC name Acetic nitric peroxyanhydride
Other names PAN peroxyacetyl nitrate α-oxoethylperoxylnitrate
Identifiers
CAS Number	2278-22-0 Y
3D model (JSmol)	Interactive image
Abbreviations	PAN
ChemSpider	15907 N
ECHA InfoCard	100.017.187
EC Number	218-905-6
PubChem CID	16782
UNII	SQ8V0P4N89 Y
CompTox Dashboard (EPA)	DTXSID4062301
InChI InChI=1S/C2H3NO5/c1-2(4)7-8-3(5)6/h1H3 N Key: VGQXTTSVLMQFHM-UHFFFAOYSA-N N
SMILES CC(OO[N+]([O-])=O)=O
Properties
Chemical formula	C2H3NO5
Molar mass	121.05 g mol−1
Solubility in water	1.46 × 10 5 mg l−1 at 298 K
log P	−0.19
Vapor pressure	29.2 mmHg at 298 K
Henry's law constant (kH)	0.000278 m3 atm mol−1 at 298 K
Atmospheric OH rate constant	10−13 cm3 molecule−1 s−1 at 298 K
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Peroxyacetyl nitrate, or PAN, is an oxidant that is more stable than ozone. Hence, it is more capable of long-range transport than ozone. It serves as a carrier for oxides of nitrogen (NOx) into rural regions and causes ozone formation in the global troposphere.^[1]

Atmospheric chemistry

PAN is produced in the atmosphere via photochemical oxidation of hydrocarbons to peroxyacetic acid radicals, which react reversibly with nitrogen dioxide (NO₂) to form PAN.^[4]: 2680 Night-time reaction of acetaldehyde with nitrogen trioxide is another possible source.^[4] Since there are no direct emissions, it is a secondary pollutant. Next to ozone and hydrogen peroxide (H₂O₂), it is an important component of photochemical smog.

Further peroxyacyl nitrates in the atmosphere are peroxypropionyl nitrate (PPN), peroxybutyryl nitrate (PBN), and peroxybenzoyl nitrate (PBzN). Chlorinated forms have also been observed. PAN is the most important peroxyacyl nitrate. PAN and its homologues reach about 5 to 20 percent of the concentration of ozone in urban areas. At lower temperatures, it is stable and can be transported over long distances, providing nitrogen oxides to otherwise unpolluted areas. At higher temperatures, it decomposes into NO₂ and the peroxyacetyl radical.

The decay of PAN in the atmosphere is mainly thermal. Thus, the long-range transport occurs through cold regions of the atmosphere, whereas the decomposition takes place at warmer levels. PAN can also be photolysed by UV radiation. It is a reservoir gas that serves both as a source and a sink of RO_x- and NO_x radicals.^[5] Nitrogen oxides from PAN decomposition enhance ozone production in the lower troposphere.

The natural concentration of PAN in the atmosphere is below 0.1 μg/m³. Measurements in German cities showed values up to 25 μg/m³. Peak values above 200 μg/m³ have been measured in Los Angeles in the second half of the 20th century (1 ppm of PAN corresponds to 4370 μg/m³). Due to the complexity of the measurement setup, only sporadic measurements are available.

PAN is a greenhouse gas.

Synthesis

PAN can be produced in a lipophilic solvent from peroxyacetic acid.^[6][7][8][9] For the synthesis, concentrated sulfuric acid is added to degassed n-tridecane and peroxyacetic acid in an ice bath. Next, concentrated nitric acid is added.

As an alternative, PAN can also be synthesized in the gas phase via photolysis of acetone and NO₂ with a mercury lamp.^[10] Methyl nitrate (CH₃ONO₂) is created as a by-product.

Toxicity

The toxicity of PAN is higher than that of ozone. Eye irritation from photochemical smog is caused more by PAN and other trace gases than by ozone, which is only sparingly soluble. PAN is a mutagen,^[11] and is considered a potential contributor to the development of skin cancer.^{[citation needed]}

References

1. Singh, H.B. (2015). "TROPOSPHERIC CHEMISTRY AND COMPOSITION | Peroxyacetyl Nitrate". In North, Gerald R.; Pyle, John A.; Zhang, Fuqing (eds.). Encyclopedia of Atmospheric Sciences. Elsevier. pp. 251–254. doi:10.1016/B978-0-12-382225-3.00433-3. ISBN 978-0-12-382225-3.
2. Finlayson-Pitts, Barbara J.; Pitts, James N. (2000). Chemistry of the Upper and Lower Atmosphere. Academic Press. ISBN 978-0-12-257060-5.^{[page needed]}
3. Meyers, Robert A. (2002). Encyclopedia of Physical Science and Technology. Elsevier Science. ISBN 978-0-12-227410-7.^{[page needed]}
4. Fischer, E. V.; Jacob, D. J.; Yantosca, R. M.; Sulprizio, M. P.; Millet, D. B.; Mao, J.; Paulot, F.; Singh, H. B.; Roiger, A.; Ries, L.; Talbot, R.W.; Dzepina, K.; Pandey Deolal, S. (14 March 2014). "Atmospheric peroxyacetyl nitrate (PAN): a global budget and source attribution". Atmospheric Chemistry and Physics. 14 (5): 2679–2698. Bibcode:2014ACP....14.2679F. doi:10.5194/acp-14-2679-2014. PMC 7983850. PMID 33758588.
5. J. S. Gaffney et al.: Peroxyacyl Nitrates. In: The Handbook of Environmental Chemistry. Vol. 4, Part B, S. 1–38; Hrsg.: Hutzinger, O., Springer, 1989.
6. Talukdar, Ranajit K.; Burkholder, James B.; Schmoltner, Anne-Marie; Roberts, James M.; Wilson, Robert R.; Ravishankara, A. R. (1995). "Investigation of the loss processes for peroxyacetyl nitrate in the atmosphere: UV photolysis and reaction with OH". Journal of Geophysical Research: Atmospheres. 100 (D7): 14163–14173. Bibcode:1995JGR...10014163T. doi:10.1029/95JD00545.
7. Nielsen, Torben; Hansen, Anne Maria; Thomsen, Erling Lund (1982). "A convenient method for preparation of pure standards of peroxyacetyl nitrate for atmospheric analyses". Atmospheric Environment. 16 (10): 2447–2450. Bibcode:1982AtmEn..16.2447N. doi:10.1016/0004-6981(82)90134-2.
8. Gaffney, J.S.; Fajer, R.; Senum, G.I. (1984). "An improved procedure for high purity gaseous peroxyacyl nitrate production: Use of heavy lipid solvents". Atmospheric Environment. 18 (1): 215–218. Bibcode:1984AtmEn..18..215G. doi:10.1016/0004-6981(84)90245-2.
9. J. L. Fry Spectroscopy and kinetics of atmospheric reservoir species: HOONO, CH₃C(O)OONO₂, CH₃OOH and HOCH₂OOH. Ph.D. Thesis, 2006
10. Warneck, Peter; Zerbach, Thomas (1992). "Synthesis of peroxyacetyl nitrate in air by acetone photolysis". Environmental Science & Technology. 26 (1): 74–79. Bibcode:1992EnST...26...74W. doi:10.1021/es00025a005.
11. "Peroxyacetyl nitrate - Hazard Genotoxicity". comptox.epa.gov. Retrieved 22 December 2024.