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Product distributions from the OH radical‐induced oxidation of n ‐pentane and isopentane (2‐methylbutane) in air
Author(s) -
Heimann Gerald,
Warneck Peter
Publication year - 2006
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.20200
Subject(s) - isopentane , chemistry , radical , isomerization , pentane , hydrogen atom abstraction , product distribution , photochemistry , cyclopentane , computational chemistry , organic chemistry , catalysis
Hydroxyl radicals, generated by photolysis of H 2 O 2 , were reacted with n ‐pentane and isopentane in air in the absence of nitrogen oxides. The observed product distributions were compared with similar data derived by computer simulations, based on the known reaction mechanisms, to determine relative probabilities for hydrogen abstraction at different sites of the parent compounds and to estimate branching ratios and relative rate coefficients for cross‐combination reactions between different peroxy radicals. For n ‐pentane, the distribution of the pentanols indicates probabilities for hydrogen abstraction, in percent, of q 1 = 9.1 ± 0.7, q 2 = 56.1 ± 1.8, and q 3 = 34.8 ± 1.3, which agree with predictions based on the algorithm proposed by Atkinson. Branching ratios needed to harmonize calculated and observed product distributions are somewhat larger than, although still within the error ranges of, the values found by us previously. Comparison between experimental and calculated data confirms the isomerization and decomposition constants recently established for the three pentoxyl radical isomers. The product distribution for isopentane, which is dominated by acetone, acetaldehyde, 2‐methyl‐butan‐2‐ol, and 2‐methyl‐butan‐2‐hydroperoxide, is in harmony with the predicted oxidation mechanism. Probabilities for hydrogen abstraction from isopentane were estimated to occur to 12% at the primary, 28% at the secondary, and 60% at the tertiary sites, again in agreement with predictions based on the algorithm of Atkinson. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 677–688, 2006