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OH Radical Initiated Reactions of Unsaturated Ketones: Kinetics and Atmospheric Implications
Bishnupriya Kar1, Balla Rajakumar1,2
1Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India.
The Journal of Physical Chemistry. A
|June 2, 2025
Summary
This study investigated the atmospheric oxidation of unsaturated ketones like 5-hexen-2-one (3BMK) and 4-hexen-3-one (E1PK) with OH radicals. Researchers determined their reaction rates and atmospheric lifetimes, identifying key degradation products.
Area of Science:
- Atmospheric Chemistry
- Chemical Kinetics
- Environmental Science
Background:
- Volatile organic compounds (VOCs) oxidation produces oxygenated organic compounds, including unsaturated ketones.
- Unsaturated ketones can affect air quality and human health.
- Understanding the atmospheric fate of these compounds is crucial.
Purpose of the Study:
- To experimentally and computationally investigate the OH radical oxidation kinetics of 5-hexen-2-one (3BMK) and 4-hexen-3-one (E1PK).
- To determine the atmospheric lifetimes and degradation products of 3BMK and E1PK.
- To enhance the comprehension of the kinetics and thermochemistry governing these reactions.
Main Methods:
- Pulsed laser photolysis - laser-induced fluorescence (PLP-LIF) technique for kinetic measurements (263-358 K, 26-30 Torr).
- Computational studies to elucidate reaction mechanisms and thermochemistry.
- Gas chromatography-mass spectrometry (GC-MS) for identifying secondary organic products.
Main Results:
- Rate coefficients at 298 K: 4.72 × 10-11 cm3 molecule-1 s-1 for 3BMK and 8.45 × 10-11 cm3 molecule-1 s-1 for E1PK.
- Temperature-dependent rate coefficients were determined and expressed using Arrhenius equations.
- Atmospheric lifetimes estimated at ~4 days for 3BMK and ~2 days for E1PK.
- Identified degradation products include 2-hydroxyacetaldehyde and acetaldehyde.
Conclusions:
- The study provides critical kinetic data for unsaturated ketones in atmospheric oxidation.
- The determined atmospheric lifetimes highlight their potential persistence and impact.
- Understanding these degradation pathways is essential for air quality modeling and health risk assessment.
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