Organic Peroxides. IV. Kinetics and Products of Decompositions of Cyclohexaneformyl and Isobutyryl Peroxides. BDPA as a Free-Radical Scavenger<sup>1</sup>

Lamb, Robert C.; Pacifici, Jas. Grady; Ayers, P. Wayne

doi:10.1021/ja01095a024

Cited by 25 publications

(6 citation statements)

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“…The decomposition of diacyl peroxides in the condensed phase generally proceeds through the formation of ion/radical pair intermediates, which undergo decarboxylation, with an ester as a primary product, as well as carboxylic acids and alcohols (21)(22)(23)(24)(25)(26)(27). The ester yield could be increased markedly by increasing the solvent polarity and the addition of common ions (25)(26)(27).…”

Section: Resultsmentioning

confidence: 99%

“…The ester yield could be increased markedly by increasing the solvent polarity and the addition of common ions (25)(26)(27). The e-folding lifetime of diacyl peroxides with respect to the first-order decomposition ranges from essentially instantaneous to several hours at room temperature (23,24,27), and the decomposition rate is accelerated with increasing solvent polarity and temperature (22)(23)(24)27). Based on measurement of decomposition rates of secondary/tertiary alkyl and phenyl diacyl peroxides in pure organic solvents (e.g., acetone), we expect that the decomposition of diacyl peroxide homologs produced in the α-pinene+O 3 system proceeds rapidly (shorter than the SOA formation timescale) in the organic, water, and ammonium sulfate aerosol mixture.…”

Section: Resultsmentioning

confidence: 99%

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Formation and evolution of molecular products in α-pinene secondary organic aerosol

Zhang

McVay

Huang

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

272

401

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Much of our understanding of atmospheric secondary organic aerosol (SOA) formation from volatile organic compounds derives from laboratory chamber measurements, including mass yield and elemental composition. These measurements alone are insufficient to identify the chemical mechanisms of SOA production. We present here a comprehensive dataset on the molecular identity, abundance, and kinetics of α-pinene SOA, a canonical system that has received much attention owing to its importance as an organic aerosol source in the pristine atmosphere. Identified organic species account for ∼58-72% of the α-pinene SOA mass, and are characterized as semivolatile/low-volatility monomers and extremely low volatility dimers, which exhibit comparable oxidation states yet different functionalities. Features of the α-pinene SOA formation process are revealed for the first time, to our knowledge, from the dynamics of individual particle-phase components. Although monomeric products dominate the overall aerosol mass, rapid production of dimers plays a key role in initiating particle growth. Continuous production of monomers is observed after the parent α-pinene is consumed, which cannot be explained solely by gasphase photochemical production. Additionally, distinct responses of monomers and dimers to α-pinene oxidation by ozone vs. hydroxyl radicals, temperature, and relative humidity are observed. Gas-phase radical combination reactions together with condensed phase rearrangement of labile molecules potentially explain the newly characterized SOA features, thereby opening up further avenues for understanding formation and evolution mechanisms of α-pinene SOA.secondary organic aerosol | particulate matter | air quality | climate S econdary organic aerosol (SOA), comprising a large number of structurally different organic oxygenates, is a dominant constituent of submicrometer atmospheric particulate matter (1). Molecular characterization of SOA has been a major research goal in atmospheric chemistry for several decades (2), owing to the importance of organic aerosol in air quality and Earth's energy budget. Both biogenic (e.g., isoprene, monoterpenes) and anthropogenic (e.g., aromatics, large alkanes) organic compounds are well-established precursors to SOA. Knowledge of the SOA molecular composition is crucial for elucidation of its underlying formation mechanisms.The most abundant monoterpene in the troposphere is α-pinene (3). The oxidation of α-pinene by ozone has become a canonical SOA system (4-12). Identification of multifunctional particlephase products has been reported, including monomers with carboxylic acid moieties (4, 6) and high-molecular-weight compounds (7,8,12), although molecular structures and formation pathways of oligomers remain uncertain (5). Recently, a class of extremely low-volatility gas-phase organic compounds (ELVOCs) has been identified as an important component in the α-pinene ozonolysis chemistry (13). Identification of the ELVOCs in the particle phase and elucidation of the mechanism of their format...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Formation and evolution of molecular products in α-pinene secondary organic aerosol

Zhang

McVay

Huang

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

272

401

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“…43 We note the concentration of active h 21 -BDPA radical in commercial samples was only 50% of the anticipated value, as determined by measuring the extinction coefficient via UV−vis experiments (see Figure S34a and Table S1). 68 Using matrixassisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS), a significant fraction of the samples were determined to be hydroxylated BDPA (HO-BDPA) and hydroperoxylated BDPA (HO-O-BDPA). These impurities were readily removed from the sample by using silica gel chromatography, and the purity of the radical was verified by further UV−vis experiments (see Figure S34b); however, subsequent exposure of purified BDPA radical to air resulted in rapid formation of the hydroxylated species, as suggested in a previous publication.…”

Section: Discussionmentioning

confidence: 99%

Overhauser Dynamic Nuclear Polarization with Selectively Deuterated BDPA Radicals

Delage-Laurin

Palani²,

Golota³

et al. 2021

J. Am. Chem. Soc.

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The Overhauser effect (OE), commonly observed in NMR spectra of liquids and conducting solids, was recently discovered in insulating solids doped with the radical 1,3-bisdiphenylene-2-phenylallyl (BDPA). However, the mechanism of polarization transfer in OE-DNP in insulators is yet to be established, but hyperfine coupling of the radical to protons in BDPA has been proposed. In this paper we present a study that addresses the role of hyperfine couplings via the EPR and DNP measurements on some selectively deuterated BDPA radicals synthesized for this purpose. Newly developed synthetic routes enable selective deuteration at orthogonal positions or perdeuteration of the fluorene moieties with 2 H incorporation of >93%. The fluorene moieties were subsequently used to synthesize two octadeuterated BDPA radicals, 1,3-[α,γ-d 8 ]-BDPA and 1,3-[β,δ-d 8 ]-BDPA, and a BDPA radical with perdeuterated fluorene moieties, 1,3-[α,β,γ,δ-d 16 ]-BDPA. In contrast to the strong positive OE enhancement observed in degassed samples of fully protonated h 21 -BDPA (ε ∼ +70), perdeuteration of the fluorenes results in a negative enhancement (ε ∼ −13), while selective deuteration of αand γ-positions (a iso ∼ 5.4 MHz) in BDPA results in a weak negative OE enhancement (ε ∼ −1). Furthermore, deuteration of βand δ-positions (a iso ∼ 1.2 MHz) results in a positive OE enhancement (ε ∼ +36), albeit with a reduced magnitude relative to that observed in fully protonated BDPA. Our results clearly show the role of the hyperfine coupled α and γ 1 H spins in the BDPA radical in determining the dominance of the zero and double-quantum cross-relaxation pathways and the polarization-transfer mechanism to the bulk matrix.

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“…Isomer 1 (R = CH3) was removed by further elution with a 20% ether-petroleum ether solution. Isomer 2 (R = CH3) showed the following: nmr (CC14) r 6.40 multiplet (2 H, CflCH3), 8.32 multiplet (8 Isomer 1 (R = CH3) showed the following: nmr (CC14) r 6.15 multiplet (2 H, CflCH3), 8.32 multiplet (8 H, CH2), 8.52 doublet (6 H, CH,CH, J = 6 Hz).…”

Section: Resultsmentioning

confidence: 99%

Syntheses and photochemistry of eight-membered cyclic azo compounds

Overberger¹,

Stoddard²

1970

J. Am. Chem. Soc.

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The preparation of the cis and trans isomers of 3,8-dimethyl-c«-l,2-diaza-l-cyclooctene (1 and 2, R = CHs) and the synthesis of cis-1,2-diaza-1 -cyclooctene (3) are described. The irradiation of these compounds and of /rani-l,2-diphenyl-cz's-l,2-diaza-l-cyclooctene (2, R = C6H5) in the presence and in the absence of triplet sensitizers is also discussed. In all cases, differences in the amounts of disproportionation and coupled products were noted when product distributions observed in the sensitized reactions were compared with those of the nonsensitized photolyses. These variations in product ratios were rationalized in terms of spin-correlation effects.Recently, there has been considerable interest in the .(1) This is the 47th in a series of papers concerned with the preparation and decomposition of azo compounds. For the previous paper, see

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Organic Peroxides. IV. Kinetics and Products of Decompositions of Cyclohexaneformyl and Isobutyryl Peroxides. BDPA as a Free-Radical Scavenger¹

Cited by 25 publications

References 0 publications

Formation and evolution of molecular products in α-pinene secondary organic aerosol

Formation and evolution of molecular products in α-pinene secondary organic aerosol

Overhauser Dynamic Nuclear Polarization with Selectively Deuterated BDPA Radicals

Syntheses and photochemistry of eight-membered cyclic azo compounds

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Organic Peroxides. IV. Kinetics and Products of Decompositions of Cyclohexaneformyl and Isobutyryl Peroxides. BDPA as a Free-Radical Scavenger1

Cited by 25 publications

References 0 publications

Formation and evolution of molecular products in α-pinene secondary organic aerosol

Formation and evolution of molecular products in α-pinene secondary organic aerosol

Overhauser Dynamic Nuclear Polarization with Selectively Deuterated BDPA Radicals

Syntheses and photochemistry of eight-membered cyclic azo compounds

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Product

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Organic Peroxides. IV. Kinetics and Products of Decompositions of Cyclohexaneformyl and Isobutyryl Peroxides. BDPA as a Free-Radical Scavenger¹