Volatile organic compounds (VOCs) are one of the critical ingredients of atmospheric pollution. Interestingly, photodissociation or thermal dissociation of VOCs produces highly reactive and unstable species. For example, the long-bonding complex in methoxy iso-nitrosyl (CH3O—ON) was predicted to be an essential atmospheric reaction complex of photodissociation of alkyl nitrites. However, the influence of the long bonding in the dynamics was understudied; thus, a thorough analysis was needed. According to the CCSD(T)/aug-cc-pVTZ level results, Hydrogen(H) atom transfer from CH3O● to NO● is thermodynamically more favorable by 15.3 kJ/mol through the IC pathway compared to the AI pathway. The electronic energy profile of H atom transfer illustrates that O—O long-bonding interaction greatly assists the reaction, but the long bonding is weaker in the (cis-1)‡. The inconsistency between the structural features and the energy profile was addressed by Valence Bond (VB) resonance structures of CH3O—ON. The VB analysis indicates that an iso-coordinated long bond is essential to carry out the H atom transfer reaction, and Natural Resonance Theory showed that the long bonding plays a key role in the IC pathway. The simplified Semi-quantitative VB (SVB) model with a long bonding resonance structure indicates that the H transfer is feasible through the IC pathway, but the triplet repulsion destabilized cis-1 and (cis-1)‡. After adding 50 resonance structures SVB analysis, the trans-1, (trans-1)‡, cis-1 and (cis-1)‡ resonance energy calculation showed that cis-1 and (cis-1)‡ are stable compared to trans-1 and (trans-1)‡, respectively, and H atom transfer is favorable through the IC pathway. Furthermore, SVB analysis demonstrated that (cis-1)‡ obtain resonance stability; hence, the transition state is stabilized by aromaticity. The aromaticity in (cis-1)‡ was further confirmed by the Electron Localization Function analysis and the Hückel theorem. In conclusion, iso-coordination long-bonding can significantly affect the H atom transfer mechanisms and lower the activation barrier.

Aromatic long-bonded methoxide isonitrosyl transition states catalyze the H atom transfer reaction

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.