The Under-Explored Possibilities of Ground State Carbonyl Photochemistry

15 September 2020, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Carbonyls are among the most abundant volatile organic compounds in the atmosphere, and their C=O chromophores allow them to photolyse. However, carbonyl photolysis reactions are not restricted to the excited state: the C=O chromophore allows relaxation to, and reaction on, the ground state, following photon absorption.

In this paper, the energetic thresholds for eight ground state reactions across twenty representative carbonyl species are calculated using double-hybrid density functional theory. Most reactions are found to be energetically accessible within the maximum photon energy available in the troposphere, but are absent in contemporary atmospheric chemistry models.

Structure–activity relationships are then elucidated so that the significance of each reaction pathway for particular carbonyl species can be predicted based upon their class. The calculations here demonstrate that ground state photolysis pathways are ubiquitous in carbonyls and should not be ignored in the analysis of carbonyl photochemistry.

Keywords

Atmospheric chemistry
Carbonyl photolysis
Ground state photochemistry
Photolytic H2
Atmospheric chemistry modelling
Decarbonylation
Ketene formation
Triple Fragmentation
Keto-enol tautomerisation

Supplementary materials

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SI Rowell The under explored possibilities of ground state carbonyl photochemistry
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SI GS paper geoms
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