Hydroxyl radical unsaturated hydrocarbons

NMHC. A large number of hydrocarbons are present in petroleum deposits, and their release during refining or use of fuels and solvents, or during the combustion of fuels, results in the presence of more than a hundred different hydrocarbons in polluted air (43,44). These unnatural hydrocarbons join the natural terpenes such as isoprene and the pinenes in their reactions with tropospheric hydroxyl radical. In saturated hydrocarbons (containing all single carbon-carbon bonds) abstraction of a hydrogen (e,g, R4) is the sole tropospheric reaction, but in unsaturated hydrocarbons HO-addition to a carbon-carbon double bond is usually the dominant reaction pathway. 

Medven, Z., H. Glisten, and A. Sabjic. 1996. Comparative QSAR study on hydroxyl radical reactivity with unsaturated hydrocarbons PLS versus MLR. J. Chemometrics 10 135-147. 

On the other hand, the indirect type of ozonation is due to the reactions of free radical species, especially the hydroxyl radical, with the organic matter present in water. These free radicals come from reaction mechanisms of ozone decomposition in water that can be initiated by the hydroxyl ion or, to be more precise, by the hydroperoxide ion as shown in reactions (4) and (5). Ozone reacts very selectively through direct reactions with compounds with specific functional groups in their molecules. Examples are unsaturated and aromatic hydrocarbons with substituents such as hydroxyl, methyl, amine groups, etc. [45,46],... 

Medven, Z., Glisten, H. and Sabljic, A. (1996). Comparative QSAR Study on Hydroxyl Radical Reactivity with Unsaturated Hydrocarbons PLS versus MLR. J.Chemom., 10,135-147. 

Reaction 7.24 is illustrative of abstraction reactions in which an atom of H is abstracted from a hydrocarbon. The hydroxyl radical product of this reaction, HO-, is very active in carrying out abstraction reactions. Even faster addition reactions are possible with alkene hydrocarbons that have unsaturated C=C bonds. For example, hydroxyl radical adds to a molecule of propene... 

---