Peroxyacyl Nitrates PANs

The class of compounds of general formula RC(0)00N02 called peroxyacyl nitrates (PANs) was first discovered in the early 1950s as components of photochemical smog. The first two compounds in the series are 

Peroxyacetyl nitrate is the first compound in the series of PANs, which itself is usually called PAN. One route of formation of PAN is the OH reaction with acetaldehyde  

Since the second reaction is very fast, it can be combined with reaction 1  

As do other peroxy radicals, the peroxyacetyl radical, CH3C(0)02, reacts with NO  

we can incorporate the fast reaction into its precursor to give CH3C(0)02 + NO N02 + CH302 + C02 

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Gaffney, J. S., N. A. Marley, and E. W. Prestbo, Peroxyacyl Nitrates (PANs) Their Physical and Chemical Properties, in The Handbook of Environmental Chemistry (O. Hutzinger, Ed.), Vol. 4, Part B, pp. 4-38, Springer-Verlag, Berlin, 1989. 

The worst irritants in photochemical smogs are peroxyacyl nitrates, PAN. They produce singlet oxygen when they hydrolyze, and this may account for their biological action. Other objectionable components of photochemical smogs include aldehydes, organic hydroperoxides (ROOH), and peroxynitrates. 

Determination of several atmospheric oxidant species is critical to understanding gaseous and aqueous processes leading to acidic deposition. Hydrogen peroxide has a high Henry s Law solubility and must be measured in gaseous and aqueous atmospheric samples to better understand wet deposition processes. In contrast, measurements of ozone and peroxyacyl nitrates (PANs) (and probably alkyl hydroperoxides and peracids) usually need to be made only in the gas phase due to their low aqueous solubility (14). 

The free radical R02 can react with 02 and N02 to produce peroxyacyl nitrate (PAN) ... 

Ozone is a powerful oxidizing agent that damages rubber, plastic materials, and all plant and animal life. It also reacts with hydrocarbons from automobile exhaust and evaporated gasoUne to form secondary organic pollutants such as aldehydes and ketones (Section 27-11). The peroxyacyl nitrates (PANs), perhaps the worst of the secondary pollutants, are especially damaging photochemical oxidants that are very irritating to the eyes and throat. 

Other harmful compounds, such as peroxyacyl nitrates (PANs), respiratory and eye irritants, are also produced in photochemical smog ... 

Coincidentally, the place Plutarch suggested as best for writing a history, a city, or urban area, is where photochemical smog and associated air pollutants were first observed and peroxyacetyl nitrate (PAN) was first identified as a potentially important air pollutant. The discovery of PAN has an interesting history. It is a story based on collaboration and discussion between biologists and chemists, leading to identification of a unique family of molecules, the peroxyacyl nitrates (PANs), which are now just beginning to be appreciated as important compounds for measurement in the free troposphere, as well as in urban air. 

Chemical Formulas and Names of Some of the More Common Peroxyacyl Nitrates (PANs)... 

Gaffney, J. S., Marley, N. A., Cunningham, M. M., and Doskey, P. V., Measurements of peroxyacyl nitrates (PANs) in Mexico City implications for mega city air quality impacts on regional scales, Atmos. Environ., 33, 5003-5012, 1999. 

In the second part, comprising chapters 6 through 32, the different, major and minor elements of the environment are dealt witli. Special attention is given to volatile organic carbons (VOCs), peroxyacyl nitrates (PANs), and endocrine disrupting chemicals (EDCs). Of course, all other discussed environmental parameters are of equal importance. 

Air pollutants can affect plants both directly and indirectly. The principal phytotoxic air pollutants are ozone, nitric oxide, nitrogen dioxide, sulfur dioxide, fluorides, and peroxyacyl nitrate (PAN). Their toxic effects have been demonstrated convincingly through field measure-... 

Peroxyacyl nitrates (PANs) Photochemical oxidants in smog. 

The basis of the chemistry included in the GEOS-Chem model (Bey et al., 1999) was described by Horowitz et al. (1998). The mechanism includes explicit chemistry for methane, ethane, propane, butane, propene, and isoprene. Butane is used as a surrogate for all alkanes with carbon number > 4 and propene for alkenes > 3. This approach is based on the similarities in the yields per carbon atom of O3, HOjt (OH, HO2, RO2) and peroxyacyl nitrates for these compound classes, as discussed by Jacob et al. (1989). Three peroxyacyl nitrates PAN, PPN (a lumped peroxyacyl nitrate) and PMN (peroxymethacryloyl nitrate) are included, together with ISN2, a lumped organic hydroxynitrate, required for the isoprene mechanism and R4N2, a lumped alkyl nitrate. Seven carbonyl species are included formaldehyde, acetaldehyde, methacrolein, other aldehydes (RCHO), acetone, methylvinyl ketone, and other ketones (MEK). 

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