ISOMERIZATION OF ALKOXY RADICALS UNDER ATMOSPHERIC CONDITIONS

The reactions of the 2-hexoxy radical and the 3-hexoxy radical have been studied in a collapsible Teflon bag reactor under conditions relevant to the atmosphere. The alkoxy radicals were generated either by the photolysis of the corresponding hexyl nitrite or by the OH radical initiated photooxidation of hexane. The hexoxy radicals were chosen as model species to examine the importance of alkoxy radical isomerization versus unimolecular decomposition or reaction with oxygen. The fraction of 2-hexoxy radicals undergoing isomerization was determined directly from the analysis of the 5-hydroxyhexan-2-one product. The fraction of 3-hexoxy radicals undergoing isomerization could only be determined indirectly. The formation of products proposed to be generated from the isomerization reaction channels was observed for the first time, including 5-nitrooxyhexan-2-ol from the reaction of isomerized radicals with NO. The approximate quantitative results confirm the predicted dominance of isomerization (greater than or equal to 68%) over other reaction pathways for longer chain alkoxy radicals. The results are compared with predictions based on kinetic estimations.