Shown here are the chemical formula for peroxyacytyl nitrate (PAN) and a diagram chemists use to represent the structure of this molecule. Note the structure based on nitrogen dioxide (NO2) in the lower right segment of the PAN molecule.
Click on image for full size
Windows to the Universe original artwork by Randy Russell.

PAN (Peroxyacytyl nitrate) - C2H3O5N

PAN (Peroxyacytyl nitrate) is a toxic chemical that is an important component of smog. PAN is a gas at normal temperatures and pressures. Its chemical formula is C2H3O5N. PAN molecules are composed of carbon, hydrogen, oxygen, and nitrogen atoms.

PAN forms via the combination of other compounds in the presence of sunlight. One component of PAN is nitrogen dioxide (NO2), which comes from the exhausts of fossil fuel-burning cars and trucks, coal-burning power plants, and other industrial processes. Volatile Organic Compounds (VOCs), released to the air as fumes from gasoline, paint, solvents, and pesticides, comprise a second set of ingredients that go into the making of PAN. A series of reactions transform VOCs into other compounds. These compounds then combine with oxygen and nitrogen dioxide to form PAN. Energy from sunlight helps drive these chemical reactions via a process called photodissociation. Ozone and airborne particulates are released as byproducts during the creation of PAN.

PAN is highly reactive and is a strong oxidizing agent. It is a powerful eye irritant and is also harmful to the respiratory system. At high concentrations it is quite damaging to plant materials, which it "burns" in a chemical reaction akin to slow-motion combustion.

Last modified February 16, 2006 by Randy Russell.

You might also be interested in:

Cool It! Game

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

Photochemical Smog

Smog is a type of air pollution. Smog is a mixture of smoke and fog, hence the name (SMoke + fOG = SMOG). Victorian-era London was famous for its thick smogs, which resulted from the city's frequent, naturally...more


Most things around us are made of groups of atoms bonded together into packages called molecules. The atoms in a molecule are held together because they share or exchange electrons. Molecules are made...more

Air Pollution Sources

Air pollution comes from many different sources. Natural processes that affect air quality include volcanic activity, which produce sulfur, chlorine, and ash particulates, and wildfires, which produce...more

Volatile Organic Chemicals (VOCs)

Volatile Organic Compounds or VOCs are organic chemicals that easily vaporize at room temperature. They are called organic because they contain the element carbon in their molecular structures. VOCs include...more

Air Pollution

What do smog, acid rain, carbon monoxide, fossil fuel exhausts, and tropospheric ozone have in common? They are all examples of air pollution. Air pollution is not new. As far back as the 13 th century,...more


Oxygen is a chemical element with an atomic number of 8 (it has eight protons in its nucleus). Oxygen forms a chemical compound (O2) of two atoms which is a colorless gas at normal temperatures and pressures....more


Sometimes when a photon hits a molecule, the energy from the photon causes the molecule to break apart. Scientists use the term "photodissociation" for such events. Photodissociation plays a very important...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA