scholarly journals Comment on “A novel and facile decay path of Criegee intermediates by intramolecular insertion reactions via roaming transition states” [J. Chem. Phys. 142, 124312 (2015)]

2015 ◽  
Vol 143 (16) ◽  
pp. 167101 ◽  
Author(s):  
Lawrence B. Harding ◽  
Stephen J. Klippenstein
Keyword(s):  
Transition States ◽  
Chem Phys ◽  
Insertion Reactions ◽  
Criegee Intermediates ◽  
Decay Path

scholarly journals Kinetics of dimethyl sulfide (DMS) reactions with isoprene-derived Criegee intermediates studied with direct UV absorption

2020 ◽  
Author(s):  
Mei-Tsan Kuo ◽  
Isabelle Weber ◽  
Christa Fittschen ◽  
Jim Jr-Min Lin
Keyword(s):  
Atmospheric Chemistry ◽  
Dimethyl Sulfide ◽  
Relative Rate ◽  
Chem Phys ◽  
High Reactivity ◽  
Rate Coefficients ◽  
Visible Absorption ◽  
Criegee Intermediates ◽  
The Individual ◽  
Kinetics Of

Abstract. Criegee intermediates (CIs) are formed in the ozonolysis of unsaturated hydrocarbons and play a role in atmospheric chemistry as a non-photolytic OH source or a strong oxidant. Using a relative rate method in an ozonolysis experiment, Newland et al. [Atmos. Chem. Phys., 15, 9521–9536, 2015] reported high reactivity of isoprene-derived Criegee intermediates towards dimethyl sulfide (DMS) relative to that towards SO2 with the ratio of the rate coefficients kDMS+CI / kSO2+CI = 3.5 ± 1.8. Here we reinvestigated the kinetics of DMS reactions with two major Criegee intermediates formed in isoprene ozonolysis, CH2OO and methyl vinyl ketone oxide (MVKO). The individual CI was prepared following reported photolytic method with suitable (diiodo) precursors in the presence of O2. The concentration of CH2OO or MVKO was monitored directly in real time through their intense UV-visible absorption. Our results indicate the reactions of DMS with CH2OO and MVKO are both very slow; the upper limits of the rate coefficients are 4 orders of magnitude smaller than that reported by Newland et al. These results suggest that the ozonolysis experiment could be complicated such that interpretation should be careful and these CIs would not oxidize atmospheric DMS at any substantial level.

scholarly journals Direct kinetic measurements and theoretical predictions of an isoprene-derived Criegee intermediate

2020 ◽  
Vol 117 (18) ◽  
pp. 9733-9740 ◽  
Author(s):  
Rebecca L. Caravan ◽  
Michael F. Vansco ◽  
Kendrew Au ◽  
M. Anwar H. Khan ◽  
Yu-Lin Li ◽  
...  
Keyword(s):  
Formic Acid ◽  
Transport Model ◽  
Thermal Conditions ◽  
Chem Phys ◽  
Kinetic Measurements ◽  
Atmospheric Species ◽  
Photoionization Mass Spectrometry ◽  
Criegee Intermediates ◽  
Atmospheric Processing ◽  
Theoretical Predictions

Isoprene has the highest emission into Earth’s atmosphere of any nonmethane hydrocarbon. Atmospheric processing of alkenes, including isoprene, via ozonolysis leads to the formation of zwitterionic reactive intermediates, known as Criegee intermediates (CIs). Direct studies have revealed that reactions involving simple CIs can significantly impact the tropospheric oxidizing capacity, enhance particulate formation, and degrade local air quality. Methyl vinyl ketone oxide (MVK-oxide) is a four-carbon, asymmetric, resonance-stabilized CI, produced with 21 to 23% yield from isoprene ozonolysis, yet its reactivity has not been directly studied. We present direct kinetic measurements of MVK-oxide reactions with key atmospheric species using absorption spectroscopy. Direct UV-Vis absorption spectra from two independent flow cell experiments overlap with the molecular beam UV-Vis-depletion spectra reported recently [M. F. Vansco, B. Marchetti, M. I. Lester, J. Chem. Phys. 149, 44309 (2018)] but suggest different conformer distributions under jet-cooled and thermal conditions. Comparison of the experimental lifetime herein with theory indicates only the syn-conformers are observed; anti-conformers are calculated to be removed much more rapidly via unimolecular decay. We observe experimentally and predict theoretically fast reaction of syn-MVK-oxide with SO2 and formic acid, similar to smaller alkyl-substituted CIs, and by contrast, slow removal in the presence of water. We determine products through complementary multiplexed photoionization mass spectrometry, observing SO3 and identifying organic hydroperoxide formation from reaction with SO2 and formic acid, respectively. The tropospheric implications of these reactions are evaluated using a global chemistry and transport model.

Comment on “trans-1,2-Disiloxybenzocyclobutene, an adequate partner for the auto-oxidation: EPR/spin trapping and theoretical studies” by J. Drujon et al., Phys. Chem. Chem. Phys., 2014, 16, 7513

2017 ◽  
Vol 19 (4) ◽  
pp. 3405-3408
Author(s):  
Hans-Gert Korth ◽  
Peter Mulder ◽  
Thomas Paul
Keyword(s):  
Ring Opening ◽  
Transition States ◽  
Chem Phys ◽  
Spin Trapping ◽  
Theoretical Studies ◽  
Epr Spin Trapping ◽  
Phys Chem Chem Phys

The involvement of biradical intermediates/biradicaloid transition states in the benzocyclobutene ring opening step needs to be considered as well.

Effect of collision energy on cross sections and product alignments for the C(1D) + H2 (v = 0, j = 0) insertion reactions

2010 ◽  
Vol 88 (5) ◽  
pp. 453-457 ◽  
Author(s):  
Lihua Kang ◽  
Bin Dai
Keyword(s):  
Angular Momentum ◽  
Potential Energy ◽  
Potential Energy Surface ◽  
Cross Sections ◽  
Total Angular Momentum ◽  
Collision Energy ◽  
Energy Surface ◽  
Chem Phys ◽  
Classical Trajectory ◽  
Insertion Reactions

Quasi-classical trajectory (QCT) calculations of total reaction probabilities and vibrationally state-resolved reaction probabilities at total angular momentum J = 0 as a function of collision energy for the C(1D) + H2 (v = 0, j = 0) reactions have been performed on an ab initio potential-energy surface [ J. Chem. Phys. 2001, 115, 10701]. In addition, the integral cross sections as a function of collision energy have been carried out for the same reaction. The product rotational alignments have also been calculated, which are almost invariant with respect to collision energies.

Reactions between hydroxyl-substituted alkylperoxy radicals and Criegee intermediates: correlations of the electronic characteristics of methyl substituents and the reactivity

2017 ◽  
Vol 19 (23) ◽  
pp. 15073-15083 ◽  
Author(s):  
Qiangli Zhao ◽  
Fengyi Liu ◽  
Weina Wang ◽  
Chunying Li ◽  
Jian Lü ◽  
...  
Keyword(s):  
Interatomic Distance ◽  
Transition States ◽  
Spin Population ◽  
Criegee Intermediates ◽  
Alkylperoxy Radicals

Methyl substituents tune ΔE and ΔG, thereby exhibiting correlations with spin population, interatomic distance, E(2) and NPA charges in their transition states.

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