Related Experiment Video
Updated: May 8, 2026
10:59
Tracking Electrochemistry on Single Nanoparticles with Surface-Enhanced Raman Scattering Spectroscopy and Microscopy
Published on: May 12, 2023
Surface-sensitive spectrometry: new insights into radical reactions at interfaces
Zachary R Schiffman1, Yuekun Yang1, Barbara J Finlayson-Pitts1
1Department of Chemistry, University of California, Irvine, Irvine, California 92697-2025, USA. wingenit@uci.edu.
Environmental Science. Processes & Impacts
|May 7, 2026
Summary
Gas-phase radicals like HO2 and RO2 significantly alter oxidized organic particles by reacting with surface products. This competition influences particle composition, affecting air quality and environmental impacts.
Area of Science:
- Atmospheric Chemistry
- Environmental Science
Background:
- Oxidized organic particles impact air quality, but surface reactions are poorly understood.
- Interactions between surface species and gas-phase radicals are critical.
Purpose of the Study:
- Investigate the impact of HO2 and RO2 radicals on glutaric acid particle surface products.
- Understand the competition between gas-phase and surface radical reactions.
Main Methods:
- Used a flow system to react hydroxyl radicals with glutaric acid particles.
- Employed Matrix Assisted Ionization in Vacuum - Mass Spectrometry (MAIV-MS) for surface product detection.
- Varied gas-phase radical concentrations and particle size.
Main Results:
- Identified alcohols, carbonyls, hydroperoxides, organic peroxides, and a potential ester product.
- Observed significant changes in product distribution with varying radical concentrations.
- Demonstrated that gas-phase HO2 and RO2 reactions control surface-bound radical fates.
Conclusions:
- Gas-phase radical reactions are key in determining the surface composition of oxidized organic particles.
- This chemistry is crucial for understanding the environmental impact of airborne particles.
Related Concept Videos
01:11Radical Reactivity: Overview
Radicals, the highly reactive species, gain stability by undergoing three different reactions. The first reaction involves a radical-radical coupling, in which a radical combines with another radical, forming a spin‐paired molecule. The second reaction is between a radical and a spin‐paired molecule, generating a new radical and a new spin‐paired molecule. The third reaction is radical decomposition in a unimolecular reaction, forming a new radical and a spin‐paired molecule. These three...
01:16Radical Reactivity: Nucleophilic Radicals
Radicals adjacent to electron-donating groups are called nucleophilic radicals. These radicals readily react with electrophilic alkenes. The SOMO–LUMO interactions are the driving force for the reaction, where the high-energy SOMO of the electron-rich, nucleophilic radicals interacts with the low-energy LUMO of the electron-deficient, electrophilic alkenes. Such SOMO–LUMO interactions are the basis of reactive radical traps, affecting the selectivity in radical reactions. For instance, consider...
01:02Radical Reactivity: Electrophilic Radicals
Radicals adjacent to electron‐withdrawing groups are called electrophilic radicals. These radicals readily react with nucleophilic alkenes. For example, the malonate radical, in which the radical center is flanked by two electron‐withdrawing groups, reacts readily with butyl vinyl ether, which consists of an electron‐donating oxygen substituent. The reaction between electrophilic malonate radical and nucleophilic vinyl ether is favored because the radical has a low‐energy SOMO, which interacts...
01:33Radical Reactivity: Intramolecular vs Intermolecular
Radical reactions can occur either intermolecularly or intramolecularly. In an intermolecular radical reaction, a nucleophilic radical adds to an electrophilic alkene or vice versa. In such reactions, the radical and generally the alkene, which is also called the radical trap, are two different molecules. Additionally, for such intermolecular reactions to occur, the radical trap must be active, present in an excess concentration, and the radical starting material must have a weak carbon–halogen...
01:10Radical Reactivity: Steric Effects
The presence of electron-donating, electron-withdrawing, or conjugating groups adjacent to a radical center, imparts electronic stabilization to the radicals. Examples of such electronically-stabilized radicals are triphenylmethyl, tetramethylpiperidine‐N‐oxide, and 2,2‐diphenyl‐1‐picrylhydrazyl. These radicals are remarkably stable and are known as persistent radicals. Some of the persistent radicals can even be isolated and purified.
Along with electronic factors, steric factors also account...
Along with electronic factors, steric factors also account...
01:20Radical Reactivity: Concentration Effects
In a radical reaction, the concentration of starting materials governs the selectivity of a radical. For example, the reaction between an alkyl halide and an alkene, in the presence of tin hydride and AIBN, begins with the generation of a tin radical. The generated radical then abstracts halogen from the alkyl halide, producing an alkyl radical. This alkyl radical can either react with tin hydride, yielding an alkane, or add to an alkene, generating a nitrile-stabilized radical, eventually...