A volatile organic compounds whose formula is C₅H₁₀O. It is released from combustion exhaust and solvent use. This is a compound that undergoes photolysis around the wavelengths of 302-320 nm and produces the acyl radical. That reactive species reacts with molecular oxygen to form a peroxide which can oxidise NO to NO₂ :

CH₃CH₂C(=O)CH₂CH₃ + hv ---> CH₃CH₂C(=O)^. + CH₃CH₂^.

CH₃CH₂C(=O). + O₂ ---> CH₃CH₂C(=O)O₂^.

CH₃CH₂C(=O)O₂^. + NO ---> NO₂ + CH₃CH₂CO₂^.

And finally the acylate radical CH₃CH₂CO₂^. can further oxidise NO to NO₂, providing even more ammunition to make ozone while the sun shines (see nitrogen dioxide and ozone). ~Subramanian, M. S. ; Environmental Chemistry Analysis; Module 3. 3 Organic Air Pollutants; Department of CHemistry; India Institute of Technology, Madras, India`