Reaction between propionaldehyde and hydroxyperoxy radical in the atmosphere: A reaction route for the sink of propionaldehyde and the formation of formic acid

Quantitative kinetics reveal that reactions of HO2 are a significant sink for aldehydes in the atmosphere and may initiate the formation of highly oxygenated molecules via autoxidation

“…The calculated enthalpy of activation for R1 with standard vibrational-frequency scaling is −1.67 kcal mol −1 , which is similar to the values of −1.03, −1.17, and −1.86 kcal mol −1 in the HO 2 reaction with HCHO, CH 3 CHO, and C 2 H 5 CHO, respectively. 28,29 This shows that the carbon chain length in aldehydes has only a minor influence on the enthalpies of activation for reaction with HO 2 .…”

“…Aldehydes are understood to undergo photolysis 18 and reaction with OH during the daytime 19 and to mainly react with nitrate radicals (NO 3 ) during the nighttime -where the OH concentration is very low (o10 4 molecules cm À3 ) [20][21][22] and there is no photolysis. 23 Previous investigations have shown that some small aldehydes [24][25][26][27][28][29] and ketones 30 can react with HO 2 . The initial reaction proceeds by forming an adduct between HO 2 and the aldehyde or ketone as in HO 2 + HCHO -HOCH 2 OO or HOOCH 2 O.…”

“…However, studies of the kinetics of HO 2 reactions with aldehydes are limited to small aldehydes such as formaldehyde and acetaldehyde, with estimated rate constants on the order of 10 À14 cm 3 molecule À1 s À1 . 28,29,31,32 It is unknown whether similar reactions can occur as rapidly even more rapidly for heavier aldehydes.…”