Addition and regeneration of OH in the presence of O2 and NO: results of naphtalene, isoprene and acetylene

The hydroxyl radical plays a major role in the tropospheric oxidation of organic compounds: In reacting with VOCs it initiates organic radical chemistry which leads to first (non-radical) products by either chain propagation (attributes 'radical' and 'odd H' are recovered in a HOx radical) or chain termination (RO2+RO2/HO2, or ROx+NOx - N-compound). Key questions about tropospheric ozone and the oxidizing capacity of the troposphere are (i) how many NO molecules are oxidized to NO2 up to first products? (ii) what are those products and what is their fate? (iii) what is the mean chain length, the turnover in OH catalyzed VOC oxidation, i.e., how much tropospheric ozone (leading to OH by photolysis) is needed to cope with VOC emissions? Unfortunately, different experimental methods - each limited in P, T, and concentration ratios (especially NO/O2, ROx/NO) - tend to give different answers; change to tropospheric conditions may again alter NO2 yield, product distribution and chain length