The theoretical study of the oxidation reaction of hydroxyl radical for the removal of volatile organic aliphatic and aromatic aldehydes from the atmosphere

High levels of volatile or semivolatile organic chemicals are released yearly into the atmosphere. Oxidation of anthropogenic pollutants via the reaction of hydroxyl radicals is one of the most effective means of their removal from the atmosphere. This computational study examined the mechanism of removal of aldehyde from the atmosphere via hydrogen abstraction by highly reactive hydroxide radical. The chemistry of the carbonyl bond of the aldehyde changed significantly from reactants to products. The minimum energy path (MEP) analysis with the kinetic study shows that the reaction for the abstraction of hydrogen from the aldehyde is both thermodynamically and kinetically favourable. The hydrogen abstraction of the aromatic aldehydes especially without methyl substituents is more kinetically favourable compared to the other aldehyde in the order of aromatic (without methyl or meta methyl) > alkane (short chain) > diene > long-chain aldehyde compounds. The entropy favours both the kinetic and thermodynamic of the aliphatic over the aromatic aldehyde compounds. The natural energy decomposition analysis (NEDA) of the interaction energy of the aldehyde and hydroxide radical also shows that a more favourable interaction of the reaction species is obtained for those that are thermodynamically favourable especially the interaction of the two components of reactants compared to those of the products. The molecular electrostatic potential (MESP) analysis also shows that the reaction sites in the reactants are more prone to reaction compared to what was observed in the products and transition state when considering the value of V-min.

Automated summary

High levels of volatile or semivolatile organic chemicals are released annually into the atmosphere. Hydroxyl radical oxidation is an efficient method for removing anthropogenic pollutants from the atmosphere. This computational study investigated the mechanism of aldehyde removal from the atmosphere through hydrogen abstraction by hydroxide radicals. The results showed that the abstraction of hydrogen from aldehyde is both thermodynamically and kinetically favorable, with aromatic aldehydes being more kinetically favorable compared to other types of aldehydes.