Ozonolysis of isoprene, one of the most abundant volatile organic compounds in the earth's atmosphere, generates the four-carbon unsaturated methacrolein oxide (MACR-oxide) Criegee intermediate. The first laboratory synthesis and direct detection of MACR-oxide is achieved through reaction of photolytically generated, resonance-stabilized iodoalkene radicals with oxygen. MACR-oxide is characterized on its first π* ← π electronic transition using a ground-state depletion method. MACR-oxide exhibits a broad UV-visible spectrum peaked at 380 nm with weak oscillatory structure at long wavelengths ascribed to vibrational resonances. Complementary theory predicts two strong π* ← π transitions arising from extended conjugation across MACR-oxide with overlapping contributions from its four conformers. Electronic promotion to the 1ππ* state agrees well with experiment, and results in nonadiabatic coupling and prompt release of O D products observed as anisotropic velocity-map images. This UV-visible detection scheme will enable study of its unimolecular and bimolecular reactions under thermal conditions of relevance to the atmosphere.
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http://dx.doi.org/10.1021/jacs.9b05193 | DOI Listing |
Chem Res Toxicol
December 2024
Department of Environmental Toxicology, University of California Davis, Davis, California 95616, United States.
Vaping cannabinoids in electronic (e)-cigarette devices is rapidly increasing in popularity, particularly among adolescents, although the chemistry affecting the composition of the vape aerosol is not well understood. This work investigates the formation of aerosol mass, bioactive hydroxyquinones, and harmful or potentially harmful carbonyls from the e-cigarette vaping of natural and synthetic cannabinoids e-liquids in propylene glycol and vegetable glycerin (PG/VG) solvent at a 50 mg/mL concentration in a commercial fourth-generation vaping device. The following cannabinoids were studied: cannabidiol (CBD), 8,9-dihydrocannabidiol (H2CBD), 1,2,8,9-tetrahydrocannabidiol (H4CBD), cannabigerol (CBG), and cannabidiolic acid (CBDA).
View Article and Find Full Text PDFPhotochem Photobiol
August 2024
University of Louisiana at Lafayette, Lafayette, Louisiana, USA.
Biogenic hydrocarbons are emitted into the Earth's atmosphere by terrestrial vegetation as by-products of photosynthesis. Isoprene is one such hydrocarbon and is the second most abundant volatile organic compound emitted into the atmosphere (after methane). Reaction with ozone represents an important atmospheric sink for isoprene removal, forming carbonyl oxides (Criegee intermediates) with extended conjugation.
View Article and Find Full Text PDFMolecules
April 2024
Shandong Mingsheng Environmental Protection Technology Co., Ltd., Jinan 250000, China.
The water produced during the oxidative esterification reaction occupies the active sites and reduces the activity of the catalyst. In order to reduce the influence of water on the reaction system, a hydrophobic catalyst was prepared for the one-step oxidative esterification of methylacrolein (MAL) and methanol. The catalyst was synthesized by loading the active component Au onto ZnO using the deposition-precipitation method, followed by constructing the silicon shell on Au/ZnO using tetraethoxysilane (TEOS) to introduce hydrophobic groups.
View Article and Find Full Text PDFEnviron Pollut
June 2024
Emissions, Measurements, and Modeling of the Atmosphere (EMMA) Laboratory, CAR, Faculty of Sciences, Saint Joseph University, Beirut, Lebanon; Climate and Atmosphere Research Center, The Cyprus Institute, Nicosia, Cyprus.
Highly resolved measurements of primary and secondary oxygenated volatile organic compounds (OVOCs) by proton-transfer-reaction mass spectrometry (PTR-MS) and the AMOVOC sampler (Airborne Measurements Of VOC) were performed in Beirut, Lebanon, during the ECOCEM (Emissions and Chemistry of Organic Carbon in the East Mediterranean) experiments. The OVOC concentrations (0.15-7.
View Article and Find Full Text PDFInt J Mol Sci
March 2024
Department of Pharmacy (DIFAR), University of Genoa, Viale Cembrano, 4, 16148 Genoa, Italy.
In tissue engineering (TE), the support structure (scaffold) plays a key role necessary for cell adhesion and proliferation. The protein constituents of the extracellular matrix (ECM), such as collagen, its derivative gelatine, and elastin, are the most attractive materials as possible scaffolds. To improve the modest mechanical properties of gelatine, a strategy consists of crosslinking it, as naturally occurs for collagen, which is stiffened by the oxidative action of lysyl oxidase (LO).
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