Rate constants for reactions of substituted methyl radicals (CH2OCH3, CH2NH2, CH2I, and CH2CN) with O2

Masaki, Akira; Tsunashima, S.; Washida, Nobuaki

doi:10.1021/j100035a014

Cited by 69 publications

(115 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…, in good agreement with the findings of Masaki et al [15] Reaction (R2) was found to have a negative temperature dependence over the 220-450 K range, described by Arrhenius parameters of, k(T) = (1.39 AE 0.01) 10…”

supporting

confidence: 91%

“…, suggesting a bimolecular reaction mechanism in agreement with the hypothesis of Masaki et al [15] but in quantitative disagreement over the rate coefficient. Enami et al [1] estimated a unity yield of IO from reaction (R2) by comparison with known yields from the reactions of O + CH 3 I and O + CF 3 I. IO was also observed following photolysis of Cl 2 /CH 3 I/O 2 /N 2 at 355 nm, showing that CH 2 I 2 is not required for the formation of IO and that CH 2 I is a direct precursor to its formation.…”

supporting

confidence: 78%

“…[23] The rate of formation of IO is also strongly dependent on the concentration of CH 2 I 2 , as shown in Figure 2, implying that IO is not generated directly from the reaction of CH 2 I + O 2 , as the concentration of O 2 is at least 17 000 times that of CH 2 I and first-order reaction conditions are present. Regression analysis of the rate of formation of IO (k' IO ) versus [CH 2 I 2 ], see Figure 2, yields an effective bimolecular rate coefficient for a reaction of CH 2 I 2 + an unknown species to form IO of k = (3.7 AE 0. , approximately 15 times smaller than that determined by Enami et al, [1]~5 0 times smaller than the more recent determination by Enami et al [2] and almost 60 times smaller than the MS determinations of Masaki et al [15] and Eskola et al [18] for the reaction of CH 2 I + O 2 . If IO is produced directly from reaction (R2) then very efficient recycling of IO would have to occur to explain this observation.…”

Section: Absorption Studiesmentioning

confidence: 55%

“…In the first direct study of the CH 2 I + O 2 reaction, Masaki et al [15] measured a pressure independent rate coefficient of (1.6 AE 0.2) 10 À12 cm 3 molecule À1 s À1 by fol-…”

mentioning

confidence: 99%

See 3 more Smart Citations

A Multidimensional Study of the Reaction CH₂I+O₂: Products and Atmospheric Implications

et al. 2010

View full text Add to dashboard Cite

The CH(2)I+O(2) reaction has been studied using laser flash photolysis followed by absorption spectroscopy, laser-induced fluorescence spectroscopy and mass spectrometry. The rates of formation of IO and CH(2)O were found to be dependent upon the concentration of CH(2)I(2) under pseudo-first-order conditions ([O(2)]≫[CH(2)I(2)]), demonstrating that IO and CH(2)O are not formed directly from the title reaction, in contrast to recent investigations by Enami et al. It is proposed that the reaction proceeds via the formation of the peroxy radical species CH(2)IO(2), which undergoes self-reaction to form CH(2)IO, and which decomposes to CH(2)O+I, and that in laboratory systems IO is formed via the reaction I+CH(2)IO(2). The absorption spectrum of a species assigned to CH(2)IO(2) was observed in the range 310-400 nm with a maximum absorption at 327.2 nm of σ≥1.7×10(-18) cm(2) molecule(-1). A modelling study enabled the room temperature rate coefficients for the CH(2)IO(2)+CH(2)IO(2) self-reaction and the I+CH(2)IO(2) reaction to be confined within the ranges (6-12)×10(-11) cm(3) molecule(-1) s(-1), and (1-2)×10(-11) cm(3) molecule(-1) s(-1), respectively. In the atmosphere, CH(2)IO(2) will slowly react with other radicals to release iodine atoms, which can then form IO via reaction with ozone. Slow formation of IO means that lower concentrations are formed, which leads to a lower propensity to form particles as the precursor molecule OIO forms at a rate which is dependent on the square of the IO concentration.

show abstract

supporting

confidence: 91%

supporting

confidence: 78%

Section: Absorption Studiesmentioning

confidence: 55%

“…In the first direct study of the CH 2 I + O 2 reaction, Masaki et al [15] measured a pressure independent rate coefficient of (1.6 AE 0.2) 10 À12 cm 3 molecule À1 s À1 by fol-…”

mentioning

confidence: 99%

See 2 more Smart Citations

A Multidimensional Study of the Reaction CH₂I+O₂: Products and Atmospheric Implications

et al. 2010

View full text Add to dashboard Cite

show abstract

“…Sunlight can efficiently induce the photolytic decomposition of CH 2 I 2 to form CH 2 I + I; the reaction of CH 2 I + O 2 eventually releases a second I atom; these I atoms might destroy ozone or become transformed to aerosol. 58,59 Even though the reaction of CH 2 I + O 2 has been investigated extensively, [52][53][54][55][56][60][61][62][63][64][65][66] a detailed mechanism of this reaction was established only recently. 67 The proposed mechanisms in the early studies were incomplete because only product channels for the formation of ICH 2 OO and H 2 CO + IO, not CH 2 OO + I, were considered.…”

Section: A Ch 2 I + Omentioning

confidence: 99%

Perspective: Spectroscopy and kinetics of small gaseous Criegee intermediates

Lee

2015

The Journal of Chemical Physics

159

122

View full text Add to dashboard Cite

The Criegee intermediates, carbonyl oxides proposed by Criegee in 1949 as key intermediates in the ozonolysis of alkenes, play important roles in many aspects of atmospheric chemistry. Because direct detection of these gaseous intermediates was unavailable until recently, previous understanding of their reactions, derived from indirect experimental evidence, had great uncertainties. Recent laboratory detection of the simplest Criegee intermediate CH2OO and some larger members, produced from ultraviolet irradiation of corresponding diiodoalkanes in O2, with various methods such as photoionization, ultraviolet absorption, infrared absorption, and microwave spectroscopy opens a new door to improved understanding of the roles of these Criegee intermediates. Their structures and spectral parameters have been characterized; their significant zwitterionic nature is hence confirmed. CH2OO, along with other products, has also been detected directly with microwave spectroscopy in gaseous ozonolysis reactions of ethene. The detailed kinetics of the source reaction, CH2I + O2, which is critical to laboratory studies of CH2OO, are now understood satisfactorily. The kinetic investigations using direct detection identified some important atmospheric reactions, including reactions with NO2, SO2, water dimer, carboxylic acids, and carbonyl compounds. Efforts toward the characterization of larger Criegee intermediates and the investigation of related reactions are in progress. Some reactions of CH3CHOO are found to depend on conformation. This perspective examines progress toward the direct spectral characterization of Criegee intermediates and investigations of the associated reaction kinetics, and indicates some unresolved problems and prospective challenges for this exciting field of research.

show abstract

Oxidation of dimethyl ether: Absolute rate constants for the self reaction of CH3OCH2 radicals, the reaction of CH3OCH2 radicals with O2, and the thermal decomposition of CH3OCH2 radicals

Sehested

Platz

et al. 1997

Int. J. Chem. Kinet.

View full text Add to dashboard Cite

The rate constant for the reaction of CH 3 OCH 2 radicals with O 2 (reaction (1)) and the self reaction of CH 3 OCH 2 radicals (reaction (5)) were measured using pulse radiolysis coupled with time resolved UV absorption spectroscopy. k 1 was studied at 296 K over the pressure range 0.025 -1 bar and in the temperature range 296 -473 K at 18 bar total pressure. Reaction (1) is known to proceed through the following mechanism:

show abstract

Rate constants for reactions of substituted methyl radicals (CH2OCH3, CH2NH2, CH2I, and CH2CN) with O2

Cited by 69 publications

References 5 publications

A Multidimensional Study of the Reaction CH₂I+O₂: Products and Atmospheric Implications

A Multidimensional Study of the Reaction CH₂I+O₂: Products and Atmospheric Implications

Perspective: Spectroscopy and kinetics of small gaseous Criegee intermediates

Oxidation of dimethyl ether: Absolute rate constants for the self reaction of CH3OCH2 radicals, the reaction of CH3OCH2 radicals with O2, and the thermal decomposition of CH3OCH2 radicals

Contact Info

Product

Resources

About

Rate constants for reactions of substituted methyl radicals (CH2OCH3, CH2NH2, CH2I, and CH2CN) with O2

Cited by 69 publications

References 5 publications

A Multidimensional Study of the Reaction CH2I+O2: Products and Atmospheric Implications

A Multidimensional Study of the Reaction CH2I+O2: Products and Atmospheric Implications

Perspective: Spectroscopy and kinetics of small gaseous Criegee intermediates

Oxidation of dimethyl ether: Absolute rate constants for the self reaction of CH3OCH2 radicals, the reaction of CH3OCH2 radicals with O2, and the thermal decomposition of CH3OCH2 radicals

Contact Info

Product

Resources

About

A Multidimensional Study of the Reaction CH₂I+O₂: Products and Atmospheric Implications

A Multidimensional Study of the Reaction CH₂I+O₂: Products and Atmospheric Implications