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1. OH, HO 2 , and RO 2 radical chemistry in a rural forest environment: measurements, model comparisons, and evidence of a missing radical sink

   https://doi.org/10.5194/acp-23-10287-2023  

   Bottorff, Brandon ; Lew, Michelle M. ; Woo, Youngjun ; Rickly, Pamela ; Rollings, Matthew D. ; Deming, Benjamin ; Anderson, Daniel C. ; Wood, Ezra ; Alwe, Hariprasad D. ; Millet, Dylan B. ; et al ( September 2024 , Atmospheric Chemistry and Physics)

   Abstract. The hydroxyl (OH), hydroperoxy (HO2), and organic peroxy (RO2)radicals play important roles in atmospheric chemistry. In the presence ofnitrogen oxides (NOx), reactions between OH and volatile organiccompounds (VOCs) can initiate a radical propagation cycle that leads to theproduction of ozone and secondary organic aerosols. Previous measurements ofthese radicals under low-NOx conditions in forested environmentscharacterized by emissions of biogenic VOCs, including isoprene andmonoterpenes, have shown discrepancies with modeled concentrations. During the summer of 2016, OH, HO2, and RO2 radical concentrationswere measured as part of the Program for Research on Oxidants:Photochemistry, Emissions, and Transport – Atmospheric Measurements ofOxidants in Summer (PROPHET-AMOS) campaign in a midlatitude deciduousbroadleaf forest. Measurements of OH and HO2 were made by laser-inducedfluorescence–fluorescence assay by gas expansion (LIF-FAGE) techniques,and total peroxy radical (XO2) mixing ratios were measured by the Ethane CHemical AMPlifier (ECHAMP) instrument. Supporting measurements ofphotolysis frequencies, VOCs, NOx, O3, and meteorological datawere used to constrain a zero-dimensional box model utilizing either theRegional Atmospheric Chemical Mechanism (RACM2) or the Master ChemicalMechanism (MCM). Model simulations tested the influence of HOxregeneration reactions within the isoprene oxidation scheme from the LeuvenIsoprene Mechanism (LIM1). On average, the LIM1 models overestimated daytimemaximum measurements by approximately 40 % for OH, 65 % for HO2,and more than a factor of 2 for XO2. Modeled XO2 mixing ratioswere also significantly higher than measured at night. Addition of RO2 + RO2 accretion reactions for terpene-derived RO2 radicals tothe model can partially explain the discrepancy between measurements andmodeled peroxy radical concentrations at night but cannot explain thedaytime discrepancies when OH reactivity is dominated by isoprene. Themodels also overestimated measured concentrations of isoprene-derivedhydroxyhydroperoxides (ISOPOOH) by a factor of 10 during the daytime,consistent with the model overestimation of peroxy radical concentrations.Constraining the model to the measured concentration of peroxy radicalsimproves the agreement with the measured ISOPOOH concentrations, suggestingthat the measured radical concentrations are more consistent with themeasured ISOPOOH concentrations. These results suggest that the models maybe missing an important daytime radical sink and could be overestimating therate of ozone and secondary product formation in this forest.

    

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2. Radical–Radical Reaction Dynamics Probed Using Millimeterwave Spectroscopy: Propargyl + NH 2 /ND 2

   https://doi.org/10.1021/acs.jpclett.1c03813  

   Gurusinghe, Ranil M. ; Dias, Nureshan ; Mebel, Alexander M. ; Suits, Arthur G. ( January 2022 , The Journal of Physical Chemistry Letters)
3. Synthesis and Oxidation of Dirhenium C 4 , C 6 , and C 8 Complexes of the Formula (η 5 -C 5 Me 5 )Re(NO)(PR 3 )(C⋮C) n (R 3 P)(ON)Re(η 5 -C 5 Me 5 ) (R = 4-C 6 H 4 R‘, c-C 6 H 11 ):  In Search of Dications and Radical Cations with Enhanced Stabilities †

   https://doi.org/10.1021/om000961m  

   Meyer, Wayne E. ; Amoroso, Angelo J. ; Horn, Clemens R. ; Jaeger, Monika ; Gladysz, J. A. ( March 2001 , Organometallics)
4. Relative energetics of CH 3 CH 2 O, CH 3 CHOH, and CH 2 CH 2 OH radical products from ethanol dehydrogenation

   https://doi.org/10.1063/5.0062809  

   Williams, Ashley E. ; Hammer, Nathan I. ; Tschumper, Gregory S. ( September 2021 , The Journal of Chemical Physics)
5. Photocatalytic Ketyl Radical Initiated C ketyl −C sp2 /C sp3 Coupling on ZnIn 2 S 4

   https://doi.org/10.1002/chem.202203785  

   Han, Chuang ; Han, Guanqun ; Habibur Rahman, Md ; Mannodi‐Kanakkithodi, Arun ; Sun, Yujie ( May 2023 , Chemistry – A European Journal)

   Visible‐light‐driven C−C bond formation utilizing ketyl radical (C_ketyl) species has attracted increasing attention recently, as it provides a direct route for the synthesis of complex molecules. However, the most‐developed homogeneous photocatalytic systems for the generation and utilization of ketyl radicals usually entail noble metal‐based (e. g., Ru and Ir) photosensitizers, which suffer from not only high cost but also potential degradation and hence pose challenges in product separation and purification. In contrast, readily accessible, inexpensive, and recyclable semiconductors represent a class of attractive and alternative photocatalysts but remain much less explored for photocatalytic ketyl radical initiated C−C bond formation. This work demonstrates that a wide range of industrially important chemicals, including substituted chromanes and tertiary alcohols, can be produced on ZnIn₂S₄under visible light irradiation through intramolecular cyclization (C_ketyl−C_sp2) and intermolecular cross‐coupling (C_ketyl−C_sp3) reactions, respectively, using ketyl radicals. A suite of experimental studies aided by computational investigation were carried out to shed light on the mechanistic insights of these two types of ketyl radical initiated C−C coupling reactions on ZnIn₂S₄.

    

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