Determination of OH, O2-, and hydroperoxide yields in ozone reactions in aqueous solution

In ozone reactions in aqueous solutions, •OH and O2•- are often generated as short-lived intermediates and hydroperoxides are formed as labile or stable final products. Tertiary butanol reacts with ozone only very slowly but readily with •OH. In the presence of dioxygen, formaldehyde is a prominent final product, 30 ± 4%, whose ready determination can be used as an assay for •OH. Although dimethyl sulfoxide reacts much more readily with ozone, its fast reaction with •OH which gives rise to methanesulfinic acid can also be applied for the determination of •OH, at least in fast ozone reactions. The formation of O2•- can be assayed with tetranitromethane (TNM), which yields nitroform anion (NF-) at close to diffusion-controlled rates. TNM is stable in neutral and acid solution but hydrolyzes in basic solution (k = 2.7 M-1 s-1), giving rise to NF- plus nitrate ion (62%) and CO2 plus 4 nitrite ions (38%). TNM reacts with O3 (k = 10 M-1 s-1), yielding 4 mol of nitrate (plus CO2) and 4 mol of O3 are consumed in ...