Atmospheric chemistry of alkanes: Review and recent developments

Alkanes comprise a significant fraction of gasolines and of the non-methane volatile organic compounds present in ambient air in urban areas. In this work, we have extended our previous studies to investigate the formation of 1,4-hydroxycarbonyls (and other products) from the reactions of OH radicals with C5–C8 n-alkanes in the absence of NO, and have investigated the rates of conversion of the commercially available 4,5-dihydro-2-methylfuran (DHMF) into 5-hydroxy-2-pentanone under various conditions in a 6900 l Teflon chamber in order to assess whether this conversion is a homogenous gas-phase or a heterogeneous wall process. We observe that the same 1,4-hydroxycarbonyls are formed in the absence of NO as in the presence of NO, but with formation yields approximately a factor of 10 lower as expected from the reaction mechanisms involved. The results of the experiments to investigate the conversion of 4,5-dihydro-2-methylfuran to 5-hydroxy-2-pentanone indicate that this conversion is not a homogeneous gas-phase process, but is a heterogeneous reaction at the chamber wall which is probably acid-catalyzed. The current understanding of the mechanisms and products of the atmospheric degradation reactions of alkanes is also presented.