An FT-IR study of the isomerization of 1-butoxy radicals under atmospheric conditions

Cassanelli, Paola; Cox, R. A.; Tyndall, Geoffrey S.

doi:10.1016/j.jphotochem.2005.11.001

Cited by 10 publications

(20 citation statements)

References 33 publications

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“…The rate coefficients for migration of Hatoms on the ring, below 10 4 s À1 for most H-migrations studied, are somewhat low compared to those in non-cyclic alkoxy radicals; for comparison, the 1,5-H-shift in 1-butoxy has a rate coefficient of B3 Â 10 5 s À1 . 40,[55][56][57] The lower rates are mostly due to the increased ring strain in the bicyclic transition state, exacerbated by the position of the radical oxygen implanted either directly on the ring or with only 1 intervening carbon. Consequently, the highest rates were found for the largest rings and hence lowest ring strain.…”

Section: Towards a Structure-activity Relationshipmentioning

confidence: 99%

A structure activity relationship for ring closure reactions in unsaturated alkylperoxy radicals

Vereecken

Wahner

et al. 2021

Phys. Chem. Chem. Phys.

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Section: Towards a Structure-activity Relationshipmentioning

confidence: 99%

A structure activity relationship for ring closure reactions in unsaturated alkylperoxy radicals

Vereecken

Wahner

et al. 2021

Phys. Chem. Chem. Phys.

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“…Our data are consistent with the isomerization rate constant from previous studies, roughly 2 × 10 5 s −1 . 15,26,[28][29][30]33,35 Although we cannot measure the kinetics of alkoxy isomerization directly from the time-resolved product appearance, we can obtain the isomerization rate from a relative rate measurement with respect to reaction with O 2 . If we assume that only reaction with O 2 (reactions 4 and 7) competes with isomerization, then we find that…”

Section: The Journal Of Physical Chemistry Amentioning

confidence: 99%

Kinetics of n-Butoxy and 2-Pentoxy Isomerization and Detection of Primary Products by Infrared Cavity Ringdown Spectroscopy

et al. 2012

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The primary products of n-butoxy and 2-pentoxy isomerization in the presence and absence of O(2) have been detected using pulsed laser photolysis-cavity ringdown spectroscopy (PLP-CRDS). Alkoxy radicals n-butoxy and 2-pentoxy were generated by photolysis of alkyl nitrite precursors (n-butyl nitrite or 2-pentyl nitrite, respectively), and the isomerization products with and without O(2) were detected by infrared cavity ringdown spectroscopy 20 μs after the photolysis. We report the mid-IR OH stretch (ν(1)) absorption spectra for δ-HO-1-C(4)H(8)•, δ-HO-1-C(4)H(8)OO•, δ-HO-1-C(5)H(10)•, and δ-HO-1-C(5)H(10)OO•. The observed ν(1) bands are similar in position and shape to the related alcohols (n-butanol and 2-pentanol), although the HOROO• absorption is slightly stronger than the HOR• absorption. We determined the rate of isomerization relative to reaction with O(2) for the n-butoxy and 2-pentoxy radicals by measuring the relative ν(1) absorbance of HOROO• as a function of [O(2)]. At 295 K and 670 Torr of N(2) or N(2)/O(2), we found rate constant ratios of k(isom)/k(O(2)) = 1.7 (±0.1) × 10(19) cm(-3) for n-butoxy and k(isom)/k(O(2)) = 3.4(±0.4) × 10(19) cm(-3) for 2-pentoxy (2σ uncertainty). Using currently known rate constants k(O(2)), we estimate isomerization rates of k(isom) = 2.4 (±1.2) × 10(5) s(-1) and k(isom) ≈ 3 × 10(5) s(-1) for n-butoxy and 2-pentoxy radicals, respectively, where the uncertainties are primarily due to uncertainties in k(O(2)). Because isomerization is predicted to be in the high pressure limit at 670 Torr, these relative rates are expected to be the same at atmospheric pressure. Our results include corrections for prompt isomerization of hot nascent alkoxy radicals as well as reaction with background NO and unimolecular alkoxy decomposition. We estimate prompt isomerization yields under our conditions of 4 ± 2% and 5 ± 2% for n-butoxy and 2-pentoxy formed from photolysis of the alkyl nitrites at 351 nm. Our measured relative rate values are in good agreement with and more precise than previous end-product analysis studies conducted on the n-butoxy and 2-pentoxy systems. We show that reactions typically neglected in the analysis of alkoxy relative kinetics (decomposition, recombination with NO, and prompt isomerization) may need to be included to obtain accurate values of k(isom)/k(O(2)).

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“…Decomposition of an alkoxy radical occurs mostly by b CÀC bond fission, and its reaction kinetics is predominantly affected by the substitution around the breaking bond. An overview of the available experimental data [6][7][8][9][10][11][12] is given by Atkinson, 5 while a number of structure-activity relationships (SARs) for prediction of rate coefficients are available; 5,[13][14][15][16] the most extensive SAR available at this time was developed by Peeters et al 13 and recently extended by Vereecken and Peeters. 15 The most important unimolecular rearrangement of alkoxy radicals is usually a 1,5-H-shift reaction, forming an OH-substituted alkyl radical; other H-migration reactions over longer or shorter spans have been proposed in chemical mechanisms.…”

Section: Introductionmentioning

confidence: 99%

A structure–activity relationship for the rate coefficient of H-migration in substituted alkoxy radicals

Vereecken

Peeters

2010

Phys. Chem. Chem. Phys.

106

205

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A framework is formulated for the development of a predictive structure-activity relationship for the temperature-dependent rate coefficients of H-migration in substituted alkoxy radicals. It is based on a multi-conformer transition state theory model, using quantum chemical characterizations of alkoxy radicals and their transition states for isomerisation. Using this framework, a SAR is then developed for the prediction of rate coefficients at 1 atm and T = 250-350 K, relative to a set of three reference reactions. The SAR covers 1,4-through 1,8-H-migration, as well as oxo- and hydroxy substitution in various positions relative to the radical oxygen and the migrating H.

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An FT-IR study of the isomerization of 1-butoxy radicals under atmospheric conditions

Cited by 10 publications

References 33 publications

A structure activity relationship for ring closure reactions in unsaturated alkylperoxy radicals

A structure activity relationship for ring closure reactions in unsaturated alkylperoxy radicals

Kinetics of n-Butoxy and 2-Pentoxy Isomerization and Detection of Primary Products by Infrared Cavity Ringdown Spectroscopy

A structure–activity relationship for the rate coefficient of H-migration in substituted alkoxy radicals

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