Autoxidation of Formaldehyde with Oxygen—A Comparison of Reaction Channels

[Image: see text] The autoxidation of formaldehyde through initiation by triplet oxygen is studied via two initial steps: (1) H-atom abstraction and (2) (3)O(2) addition reaction. The reaction energy profiles show that the reactions are thermodynamically and kinetically demanding. A comparison of the pathways of these initial reactions and the search for a less energy-demanding pathway is presented. The presence of a Brønsted acid has no effect on the energetics of the reaction, while the presence of a single water molecule catalyst enhances the initial reactions. The H-atom abstraction reaction from formaldehyde results in formyl and hydroperoxy radicals. These radicals on further reaction with the second equivalent of (3)O(2) lead to a CO + 2HO(2) product channel. The (3)O(2) addition reaction to formaldehyde results in a triplet biradical intermediate which further leads to performic acid, the precursor in the synthesis of carboxylic acids from aldehydes. In the presence of water molecules, performic acid is formed in a single kinetic step, and this leads to a CO(2) + OH + HO(2) product channel upon subsequent reaction with (3)O(2) in a thermodynamically favorable reaction. The results show that the less established (3)O(2) addition reaction to aldehydes is a viable route for autoxidation in the absence of purpose-built initiators, in addition to the well-established H-atom abstraction route.