Criegee Intermediate Chemistry in Atmospheric Reactions

Criegee intermediates are highly reactive carbonyl oxides formed during the ozonolysis of unsaturated hydrocarbons in the troposphere. Their subsequent chemistry—encompassing unimolecular rearrangements, bimolecular reactions with water monomers and dimers, sulphur dioxide, nitrogen oxides and organic substrates—affects the oxidative capacity of the atmosphere, the cycling of HOx and NOx radicals and the formation of secondary organic aerosols. The lifetimes of these intermediates are governed by a delicate balance between rapid internal decay and collisional stabilisation, with temperature, pressure and substituent effects exerting a strong influence on speciation and reactivity. Advances in spectroscopy, theoretical kinetics and global modelling have begun to resolve the contributions of individual Criegee species to regional and global processes, revealing their role in sulphuric acid production, aerosol nucleation and trace‐gas removal, and highlighting the need for accurate rate constants in chemical transport models.

Research from Nature Portfolio

Transient infrared spectroscopy has been used to obtain the first definitive mid-IR spectra of the two conformers of methyl‐substituted Criegee intermediate, syn- and anti-CH₃CHOO. High-level quantum-chemical calculations enabled precise simulation of rotational contours and unambiguous identification of both species. Kinetic measurements in the presence of NO and NO₂ demonstrated that the anti conformer reacts significantly faster than the syn form, while in the absence of these coreactants anti-CH₃CHOO also decays more rapidly via unimolecular channels. This work establishes a robust spectroscopic handle for field measurements and refines our understanding of conformer-dependent pathways in atmospheric Criegee chemistry.

Criegee Intermediate Chemistry in Atmospheric Reactions publication trend

The graph below shows the total number of articles in criegee intermediate chemistry in atmospheric reactions across all publications each year (not limited to Nature Index journals).

Technical terms

Criegee intermediate: A transient carbonyl oxide formed by the reaction of ozone with an alkene.

Stabilised Criegee intermediate (SCI): A Criegee intermediate that has been collisionally deactivated and survives long enough to undergo bimolecular reactions.

Ozonolysis: The atmospheric reaction of ozone with unsaturated organic compounds, producing Criegee intermediates.

Unimolecular decay: Internal rearrangement or decomposition of a reactive intermediate without collision with another molecule.

Water dimer: A weakly bound complex of two water molecules that can accelerate Criegee intermediate reactions.

References

1. Unimolecular Reactions of E-Glycolaldehyde Oxide and Its Reactions with One and Two Water Molecules. Research (2023).
2. Unimolecular decay strongly limits the atmospheric impact of Criegee intermediates. Physical Chemistry Chemical Physics (2017).
3. Infrared identification of the Criegee intermediates syn- and anti-CH3CHOO, and their distinct conformation-dependent reactivity. Nature Communications (2015).
4. Criegee Intermediate–Alcohol Reactions, A Potential Source of Functionalized Hydroperoxides in the Atmosphere. ACS Earth and Space Chemistry (2017).