From Glossary of Meteorology
Oxygenated compounds that are organic derivatives of hydrogen peroxide.
The simplest is methyl hydroperoxide, formula CH3OOH. These compounds are formed in the oxidation of hydrocarbons in relatively clean air, where oxides of nitrogen are not abundant. The presence of the alkyl group renders them much less soluble than hydrogen peroxide and therefore more susceptible to long-range transport in the atmosphere.