A5082800326- Atmospheric chemistry and aerosols
- Atmospheric Ozone and Climate
- Catalytic Processes in Materials Science
- Catalysis and Oxidation Reactions
- Advanced Chemical Physics Studies
- Spectroscopy and Laser Applications
- Air Quality and Health Impacts
- Air Quality Monitoring and Forecasting
- Free Radicals and Antioxidants
- Electrochemical Analysis and Applications
- Atmospheric and Environmental Gas Dynamics
- Inorganic and Organometallic Chemistry
- Photochemistry and Electron Transfer Studies
- Astronomy and Astrophysical Research
- Polyoxometalates: Synthesis and Applications
- Molecular Spectroscopy and Structure
- Indoor Air Quality and Microbial Exposure
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Contemporary Christian Leadership and Education
- Space exploration and regulation
- Wastewater Treatment and Nitrogen Removal
- Atmospheric aerosols and clouds
- Oxidative Organic Chemistry Reactions
- Chemical Reactions and Isotopes
University of Copenhagen
2015-2023
University of Colorado Boulder
2017
University of Michigan
2017
University of Cumbria
2014
Biocat
2012
Dimethyl sulfide (DMS), emitted from the oceans, is most abundant biological source of sulfur to marine atmosphere. Atmospheric DMS oxidized condensable products that form secondary aerosols affect Earth's radiative balance by scattering solar radiation and serving as cloud condensation nuclei. We report atmospheric discovery a previously unquantified oxidation product, hydroperoxymethyl thioformate (HPMTF, HOOCH2SCHO), identified through global-scale airborne observations demonstrate it be...
Atmospheric oxidation of monoterpenes (emitted primarily by evergreen trees) is known to contribute the formation and growth aerosol particles. While recent research has tied organic unimolecular chemistry peroxy radicals (RO2) formed in monoterpenes, fundamental physical these RO2 remains obscure. Here we use isomer-specific measurements ab initio calculations determine reaction rates products derived from hydroxyl radical (OH) α-pinene β-pinene. Among all structural isomers...
Based on a small test system, (R)-CH(OH)(OO·)CH2CHO, we have developed cost-effective approach to the practical implementation of multiconformer transition state theory for peroxy radical hydrogen shift reactions at atmospherically relevant temperatures. While conformer searching is crucial accurate reaction rates, an energy cutoff can be used significantly reduce computational cost with little loss accuracy. For barrier, high-level calculations are needed, but highest level electronic...
With an annual emission of about 500 Tg, isoprene is important molecule in the atmosphere. While much its chemistry well constrained by either experiment or theory, rates many unimolecular peroxy radical hydrogen-shift (H-shift) reactions remain speculative. Using a high-level multiconformer transition state theory (MC-TST) approach, we determine recommended temperature dependent reaction rate coefficients for number H-shift oxidation mechanism. We find that most (1,4, 1,5, and 1,6)...
Emissions of aromatic compounds cause air pollution and detrimental health effects. Here, we explore the reaction kinetics products key radicals in benzene photo-oxidation. After initial OH addition with O2, effective production rates phenol bicyclic peroxy radical (BCP-peroxy) are experimentally constrained at 295 K to be 420 ± 80 370 70 s–1, respectively. These lead approximately 53% yield for 47% BCP-peroxy under atmospheric conditions. The NO produces hydroxy nitrate a branching ratio...
We report chamber measurements of secondary organic aerosol (SOA) formation from isoprene photochemical oxidation, in which radical concentrations were systematically varied and the molecular composition semi- to low-volatility gases SOA measured online. Using a detailed chemical kinetics box model, we find that explain behavior products mass yields relative input H2O2 concentrations, second-generation dihydroxy hydroperoxy peroxy (C5H11O6·) must undergo an intramolecular H-shift with net...
Oxidation of monoterpenes (C10H16) by nitrate radicals (NO3) constitutes an important source atmospheric secondary organic aerosol (SOA) and organonitrates. However, knowledge the mechanisms their formation is incomplete differences in yields between similar are poorly understood. In particular, SOA organonitrates from α-pinene + NO3 low, while those Δ3-carene high. Using computational methods, we suggest that bond scission nitrooxy alkoxy lead to reactive keto-nitrooxy-alkyl radicals, which...
Autoxidation has been acknowledged as a major oxidation pathway in broad range of atmospherically important compounds including isoprene, monoterpenes, and very recently, dimethyl sulfide. Here, we present high-level theoretical multiconformer transition-state theory study the atmospheric autoxidation amines exemplified by trimethylamine (TMA) dimethylamine generalized larger diethylamine. Overall, find that initial hydrogen shift reactions have rate coefficients greater than 0.1 s–1 is thus...
Monoterpenes are a group of volatile organic compounds (VOCs) emitted to the atmosphere in large amounts. Studies have linked autoxidation monoterpenes formation secondary aerosols, which impact Earth's climate and human health. Here, we study hydroxy peroxy radicals formed by OH- O2-addition six atmospherically relevant α-pinene, β-pinene, Δ3-carene, camphene, limonene, terpinolene. The all six-membered ring but differ binding pattern four remaining carbon atoms position double bond(s). We...
Organic hydrotrioxides (ROOOH) are known to be strong oxidants used in organic synthesis. Previously, it has been speculated that they formed the atmosphere through gas-phase reaction of peroxy radicals (RO2) with hydroxyl (OH). Here, we report direct observation ROOOH formation from several atmospherically relevant RO2 radicals. Kinetic analysis confirmed rapid + OH reactions forming ROOOH, rate coefficients close collision limit. For OH-initiated degradation isoprene, global modeling...
We have observed the NH···P hydrogen bond in a gas phase complex. The is identified dimethylamine-trimethylphosphine complex by red shift of fundamental NH-stretching frequency using Fourier transform infrared spectroscopy (FT-IR). On basis measured shifts, we find that P acceptor atom similar strength to S. Both are stronger acceptors than O and significantly weaker N. angle, ∠NHP, found be very sensitive functional employed density theory (DFT) optimizations possible parameter assess...
The oxidation of biogenically emitted volatile organic compounds (BVOC) plays an important role in the formation secondary aerosols (SOA) atmosphere. Peroxy radicals (RO2) are central intermediates BVOC process. Under clean (low-NO x) conditions, main bimolecular sink reactions for RO2 with hydroperoxy radical (HO2) and other radicals. Especially small RO2, + HO2 reaction mainly leads to closed-shell hydroperoxide products. However, there exist known channels that can recycle oxidants...
Hydroxymethyl hydroperoxide (HMHP), formed in the reaction of C1 Criegee intermediate with water, is among most abundant organic peroxides atmosphere. Although OH thought to represent one important atmospheric removal processes for HMHP, this has been largely unstudied laboratory. Here, we present measurements kinetics and products HMHP OH. was oxidized by an environmental chamber; decay formation formic acid formaldehyde were monitored over time using CF3O- chemical ionization mass...
The OH + DMDS reaction mainly forms SO<sub>2</sub> and CH<sub>3</sub>O<sub>2</sub> with a yield close to two lesser extent RO<sub>2</sub> isomerization products.
Limonene is one of the monoterpenes with largest biogenic emissions and also widely used as an additive in cleaning products, leading to significant indoor emissions. Studies have found that formation secondary organic aerosols (SOAs) from limonene oxidation has important implications for air quality. Although ozonolysis considered major pathway under most conditions, little known about mechanisms SOA ozonolysis. Here, we calculate rate coefficients possible unimolecular reactions...
NO3 radical oxidation of most monoterpenes is a significant source secondary organic aerosol (SOA) in many regions influenced by both biogenic and anthropogenic emissions, but there are very few published mechanistic studies chemistry beyond simple first generation products. Here, we present computationally derived mechanism detailing the unimolecular pathways available to second peroxy radicals following Δ-3-carene, defining generations based on sequence formed rather than number oxidant...
The atmospheric oxidation mechanisms of reduced sulfur compounds are great importance in the biogeochemical cycle. CH3S radical represents an important intermediate these processes. Under conditions, will predominantly react with O2 to form peroxy CH3SOO. formed CH3SOO has two competing unimolecular reaction pathways: isomerization CH3SO2, which further decomposes into CH3 and SO2, or a hydrogen shift followed by HO2 loss, leading CH2S. Previous theoretical calculations have suggested that...
In this work, we find significant branching to an accretion product in the self-reaction of ethene-derived hydroxy peroxy radicals.
The Inflation Reduction Act is one of the most prominent cases green industrial policy. It was motivated by a strategic intention increasing popular support for both climate policy and Democratic party. Since its passage in August 2022, large private-sector investments low-carbon manufacturing have been announced many electorally pivotal areas United States. expectation that these spatially concentrated benefits would boost local pro-climate incumbent party – Democrats supported political...
Hydroperoxides are formed in significant amounts the atmosphere by oxidation of volatile organic compounds and key aerosol formation. In a room-temperature experiment, we detected formation bimolecular complexes tert-butyl hydroperoxide (t-BuOOH) corresponding alcohol tert-butanol (t-BuOH), with dimethyl ether (DME) as hydrogen-bond acceptor. Using combination Fourier-transform infrared spectroscopy quantum chemical calculations, compare strength OH-O hydrogen bond total complexation. We...
The gas phase ultraviolet spectrum and stability of 1,1-dihydroxyacetone (the geminal diol methylglyoxal) are investigated using spectroscopic computational methods. Experimental electronic spectra recorded in the ultraviolet–visible range were used to follow hydration methylglyoxal. We show that upon addition water, methylglyoxal hydrates form diol. its conformers calculated TD-DFT LR-CC methods facilitate experimental peak assignments. lowest energy transition is experimentally measured...
We show that the diastereomers of hydroxy peroxy radicals formed from OH and O2 addition to C2 C3, respectively, crotonaldehyde (CH3CHCHCHO) undergo gas-phase unimolecular aldehydic hydrogen shift (H-shift) chemistry with rate coefficients differ by an order magnitude. The stereospecificity observed here for is general will lead a significant diastereomeric-specific in atmosphere. This enhancement specific stereoisomers stereoselective reactions could have widespread implications given...
Autoxidation in the atmosphere has been realized last decade as an important process that forms highly oxidized products relevant for formation of secondary organic aerosol and likely with detrimental human health effects. It is experimentally shown OH radical-initiated oxidation trimethylamine, most emitted amine atmosphere, proceeds via rapid autoxidation steps dominating its atmospheric process. All three methyl groups are functionalized within a timescale 10 s following reaction radicals...
Oxidation of the monoterpene Δ3-carene (C