Unimolecular Decomposition of Chemically Activated <i>sec</i>-Butyl Radicals from H Atoms plus <i>cis</i>-Butene-2

Rabinovitch, B. S.; Diesen, R. W.

doi:10.1063/1.1730036

Cited by 131 publications

(43 citation statements)

References 41 publications

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“…where B(E) is the temperature dependent Boltzmann distribution of internal energy eigenstates for propylene [49]. The ratio of branching fractions, R ac ϭ ⌫ 1a / ⌫ 1c ϭ S 1 /D 1 , will exhibit both a pressure and temperature dependence.…”

Section: F(e) ϭ Kј(e)b(e)/⌺kј(e)b(e)mentioning

confidence: 99%

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.

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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

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Section: F(e) ϭ Kј(e)b(e)/⌺kј(e)b(e)mentioning

confidence: 99%

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.

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“…* have confirmed that the minimum k, for this system is 1.8X loi sec-'. Explanations for the pressure variation in k, may be found elsewhere [7]. The average quantities A(24DMP2a7 iPr.…”

Section: (B) 24dmp2 Systemmentioning

confidence: 99%

Disproportionation‐combination ratios of large branched alkyl radicals

Georgakakos

Rabinovitch

Larson

1971

Int J of Chemical Kinetics

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The disproportionation-combination reactions of radicals 4,4-dimethylpentyl-2 and 2,4-dimethylpentyl-2, produced by collisional stabilization of the respective chemically activated species, have been studied at 298"K, with and without getter radicals. Use of getters t-C4H9 and CzHs with 4,4-dimethylpentyl-2, and of iso-C3HT with 2,4-dimethylpentyl-2 yielded disproportionation-combination ratios A for parent-getter and t-C4H9-C 2H6 cross reactions, and for the mutual reaction of t-CqH9 radicals. The unstabilized hot radicals decompose, and these experiments also yielded values for the high-pressure rate constant k,, of 1.7OX 108sec-1 and 2.11 X 105ec-' for 4,4-dimethylpentyl-2 and 2,4-dimethylpentyl-2, respectively. The results, compared to those for other large alkyl radical systems obtained earlier, suggest that steric effects influence the accessibility of H atoms for transfer .

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“…n-CsH11 + n-C5HllNzCH3 -+ n-C5Hl2 + CjHloNzCH3 (20) CH3 + n-CjHlIN2CH3 + CH4 + CsHloNzCH3 (21) The rate equation which can be derived from the reaction scheme is . It was assumed that all sec-pentyl radicals result from the thermal unimolecular isomerization of n-pentyl radicals.…”

Section: Isomerization Of the N-pentyl Radicalmentioning

confidence: 99%

Photolysis of n-pentylazomethane vapor. Reactions of the n-pentyl radical

Watkins¹

1971

J. Am. Chem. Soc.

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occur t o the 3(~,7r*) state with resulting cis-trans isomerization. It is therefore not surprising that the intersystem crossing rate constant for AIP is greater than the corresponding constants for DBO and DBH, being in excess of 1O' O sec-I.' For bicyclic azo compounds, the lower intersystem rate constants may be understood in terms of a crossing to a (n,p*) rather than a (T,T*) manifold3* and less marked differences between the equilibrium geometries of the states, resulting in less favorable Franck-Condon factors. 35 In this previous work we have used sensitization extensively as a source of triplet molecules. lr7 In Table I the interaction rate constante (kir) of a variety of substrates, including azo compounds, with several triplet (38) M. A. El-Sayed, Accounrs Chem. Res., 1, 8 (1968).Abstract: The vapor-phase photolysis of n-pentylazomethane was studied in the temperature range 24-162 ' . The product rate data fit well the proposed reaction scheme involving methyl and n-pentyl radicals. Evidence for the generation of photochemically activated n-pentyl radicals was found. The implications of this evidence to previous work on the photolysis of azoalkanes are discussed. When the concentration of photochemically activated radicals was minimized, the thermal rate constants for the isomerization andH-atom abstraction reactionsof the n-pentyl radical were determined: n-C5H11 + sec-C5H11 (17), k17 = 3.3 X lo8 exp(-l5.1 X 103/RT) sec-'; n-C5H11 + n- (20), kzo = 4.2 X 10" exp(-7.8 X lO3/RT) mol-' cm3 sec-I. The disproportionation to combination ratio at 25 O for n-pentyl radicals was estimated to be 0.14, and A(Me, n-Pe) = 0.033. C~H I~N~C H~here is almost no quantitative information in the W (10) (a) R.

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Unimolecular Decomposition of Chemically Activated sec-Butyl Radicals from H Atoms plus cis-Butene-2

Cited by 131 publications

References 41 publications

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

Disproportionation‐combination ratios of large branched alkyl radicals

Photolysis of n-pentylazomethane vapor. Reactions of the n-pentyl radical

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