Rate constants for some radical-radical cross-reactions and the geometric mean rule

Garland, Leslie J.; Bayes, Kyle D.

doi:10.1021/j100375a034

Cited by 48 publications

(48 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The rate coefficient for the methyl-vinyl radical- ϫ 10 cm molecule s [40] In this case, the k 1 value overlaps with the k 17 value and both rate coefficients approximate the collisional rate. This suggests a near zero activation energy and thus a weak temperature dependence of the total rate constant for both of these cross-radical reactions.…”

Section: Discussionmentioning

confidence: 91%

“…In a thorough analysis of this approximation to six different radical-radical cross-reactions involving small hydrocarbon species, Garland and Bayes [40] caution that even for similar reactions the geometric mean rule can fail.…”

Section: Discussionmentioning

confidence: 99%

“…The 1-butene product (C 4 H 8 ) is believed to result solely from the combination channel (R19a) of the fast cross-radical reaction [36,40].…”

Section: Qualitative Ch 3 ؉ C 2 H 3 Product Observations At T ‫؍‬ 298mentioning

confidence: 99%

See 2 more Smart Citations

Rate constant and RRKM product study for the reaction between CH3 and C2H3 at T = 298 K

Thorn

Payne

Chillier

et al. 2000

Int. J. Chem. Kinet.

View full text Add to dashboard Cite

The total rate constant k 1 has been determined at P ϭ 1 Torr nominal pressure (He) and at T ϭ 298 K for the vinyl-methyl cross-radical reaction: (1) CH 3 ϩ C 2 H 3 : Products. The measurements were performed in a discharge flow system coupled with collision-free sampling to a mass spectrometer operated at low electron energies. Vinyl and methyl radicals were generated by the reactions of F with C 2 H 4 and CH 4 , respectively. The kinetic studies were performed by monitoring the decay of C 2 H 3 with methyl in excess, 6 Ͻ [CH 3 ] 0 / [C 2 H 3 ] 0 Ͻ 21. The overall rate coefficient was determined to be k 1 (298 K) ϭ (1.02 Ϯ 0.53) ϫ 10 Ϫ10 cm 3 molecule Ϫ1 s Ϫ1 with the quoted uncertainty representing total errors. Numerical modeling was required to correct for secondary vinyl consumption by reactions such as C 2 H 3 ϩ H and C 2 H 3 ϩ C 2 H 3 . The present result for k 1 at T ϭ 298 K is compared to two previous studies at high pressure (100-300 Torr He) and to a very recent study at low pressure (0.9-3.7 Torr He).Comparison is also made with the rate constant for the similar reaction CH 3 ϩ C 2 H 5 and with a value for k 1 estimated by the geometric mean rule employing values for k(CH 3 ϩ CH 3 ) and k(C 2 H 3 ϩ C 2 H 3 ). Qualitative product studies at T ϭ 298 K and 200 K indicated formation of C 3 H 6 , C 2 H 2 , and C 3 H 5 as products of the combination-stabilization, disproportionation, and combination-decomposition channels, respectively, of the CH 3 ϩ C 2 H 3 reaction. We also observed the secondary C 4 H 8 product of the subsequent reaction of C 3 H 5 with excess CH 3 ; this observation provides convincing evidence for the combination-decomposition channel yielding C 3 H 5 ϩ H. RRKM calculations with helium as the deactivator support the present and very recent experimental observations that allylic C-H bond rupture is an important path in the combination reaction. The pressure and temperature dependencies of the branching fractions are also predicted. . Reaction rate constants and product channel information are required for all such models that attempt to account quantitatively for the observed atmospheric composition and structure. Hydrocarbon photochemistry is initiated by the photodissociation of methane in the upper

show abstract

Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Rate constant and RRKM product study for the reaction between CH3 and C2H3 at T = 298 K

Thorn

Payne

Chillier

et al. 2000

Int. J. Chem. Kinet.

View full text Add to dashboard Cite

show abstract

“…. Furthermore, in the methyl-propargyl mixed radical system the radical -radical reaction products and rate constants are related by the approximate "geometric mean" relationship for pulsed experiments [13,22] ). This agreement provides additional support for the rate constant values determined here for the propargyl self-reactions (k 4 ) and propargyl-methyl crossreactions (k 5 ).…”

Section: Kinetic Modeling Of Ch 3 and C 3 H 3 Mixed Radical Systemmentioning

confidence: 99%

Kinetics and products of propargyl (C3H3) radical self-reactions and propargyl-methyl cross-combination reactions

Fahr

Nayak

2000

Int. J. Chem. Kinet.

View full text Add to dashboard Cite

Propargyl (HC#C 9 CH 2 ) and methyl radicals were produced through the 193-nm excimer laser photolysis of mixtures of C 3 H 3 Cl/He and CH 3 N 2 CH 3 /He, respectively. Gas chromatographic and mass spectrometric (GC/MS) product analyses were employed to characterize and quantify the major reaction products. The rate constants for propargyl radical self-reactions and propargyl-methyl cross-combination reactions were determined through kinetic modeling and comparative rate determination methods. The major products of the propargyl radical combination reaction, at room temperature and total pressure of about 6.7 kPa (50 Torr) consisted of three C 6 H 6 isomers with 1,5-hexadiyne(CH # C 9CH 2 9CH 2 9C #CH, about 60%); 1,2-hexadiene-5yne (CH 2 " C "C9CH 2 9C#CH, about 25%); and a third isomer of C 6 H 6 (ϳ15%), which has not yet been, with certainty, identified as being the major products. The rate constant determination in the propargyl-methyl mixed radical system yielded a value of (4.0 Ϯ 0.4) ϫ 10 Ϫ11 cm 3 molecule Ϫ1 s Ϫ1 for propargyl radical combination reactions and a rate constant of (1.5 Ϯ 0.3) ϫ 10 Ϫ10 cm 3 molecule Ϫ1 s Ϫ1 for propargyl-methyl cross-combination reactions. The products of the methyl-propargyl cross-combination reactions were two isomers of C 4 H 6 , 1-butyne (about 60%) and 1,2-butadiene (about 40%).

show abstract

“…For polar radicals such as CH 3 O and CH 2 COCH 3 [7], or radicals not derived from hydrocarbons, like FS(O 2 )O and FC(O)O [8], φ lies far away from 2, such that the cross-combination rule does not apply. Even for many hydrocarbon radicals, φ = 2 may be calculated [1].…”

Section: Introductionmentioning

confidence: 99%

Analytical resolution of a parallel second‐order reaction mechanism

Croce

Mogni

Irrazábal

2003

Int J of Chemical Kinetics

View full text Add to dashboard Cite

The competition among the three different elementary second-order processes involving the radicals A and B,is frequently established in many combustion and atmospheric chemistry systems. The analytical resolution of the above mechanism for k AB = 2k AA and k AB = 2k BB , that is, for a crosscombination ratio φ = k AB /(k AA k BB ) 1/2 = 2, is well-known, but it has been claimed not to exist for φ = 2. In the present paper an analytical resolution of the system (1)- (3), performed under the condition k AB = 2k AA and k AB = 2k BB , leads toThe mathematical procedure leading to this equation and the equation itself are valid independently of the nature of the products of the reactions (1), (2), and (3), that is, recombination or disproportionation products, provided that the reactants and the order of the reactions remain the same.

show abstract

Rate constants for some radical-radical cross-reactions and the geometric mean rule

Cited by 48 publications

References 1 publication

Rate constant and RRKM product study for the reaction between CH3 and C2H3 at T = 298 K

Rate constant and RRKM product study for the reaction between CH3 and C2H3 at T = 298 K

Kinetics and products of propargyl (C3H3) radical self-reactions and propargyl-methyl cross-combination reactions

Analytical resolution of a parallel second‐order reaction mechanism

Contact Info

Product

Resources

About