Recently, Professor Bo Long works in our university and his collaborators studiedan unexpectedly fast mechanistic pathway for the unimolecular reactionsof large Criegee intermediates by theoretical calculation methods, supported by the National Natural Science Foundation of China (41775125), according to NSFS’s web reported. These results find that stable Criegee intermediates containing five or six carbon atoms with a carbonyl group have much lower atmospheric oxidation capacity. The results are entitled "Rapid unimolecular reaction of stabilized Criegee intermediates and implications for atmospheric chemistry", published inNature Communications. (https://www.nature.com/articles/s41467-019-09948-7.)
Criegee intermediates are produced in the ozonolysis of alkenes, which are involved in several key atmospheric chemical processes such as the formation of hydroxyl radicals, sulfuric acid, highly oxygenated organic molecules, and olefins, etc. They have an important impacts on the atmospheric oxidation capacity and the formation of new nanoparticles, and play a key role in the process of atmospheric complex pollution. However, due to the complex electronic structures and short lifetimes of Criegee intermediates, it is a bigger challenge for both theoretical and experimental research; leads to the lack of relevant kinetic parameters and reaction mechanism informations, which makes the relevant researches still a hot topic in current atmospheric chemistry community.
Professor Bo Long and his collaborators studied the different structures of Criegee intermediates and its atmospheric lifetimes by using very recently developed density functional method and energy composite calculation method. The calculation results reveal the impacts of Criegee intermediates on their atmospheric oxidation capacity. The results show that the stable Criegee intermediates containing five or six carbon atoms of carbonyl group have an unexpectedly fast unimolecular reactions pathway, and the calculation rate constants show that the mechanistic pathways are faster five orders of magnitude than those of the corresponding hydrogen shift processes. This limits that the class of Criegee intermediates can not oxidizeSO2to SO3to form sulfuric acid, and there is no the formation of hydroxyl radical in unimolecular reactions pathway. The findings indicated that this kind of Criegee intermediates have a significantly low atmospheric oxidation capacity. (as shown in the figure) The results of this paper can provide key parameters for pollution model and important basis for clarifying the formation mechanism of atmospheric complex pollution.
Nature Communications, one of the top journals in all fields, has strict quality requirements. The above research work involves a large amount of experimental work and cautious repetitive verification work. Professor Bo Long and his team have been solved various research problems through years of painstaking research work, during which they have achieved today's results.