Premium
Isomerization reactions of the n ‐C 4 H 9 O and n ‐OOC 4 H 8 OH radicals in oxygen
Author(s) -
Heiss Adolphe,
Sahetchian Krikor
Publication year - 1996
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/(sici)1097-4601(1996)28:7<531::aid-kin5>3.0.co;2-w
Subject(s) - butyraldehyde , chemistry , radical , isomerization , photochemistry , reaction rate constant , decomposition , oxygen , kinetics , organic chemistry , catalysis , physics , quantum mechanics
Reactions of n ‐C 4 H 9 O radicals have been investigated in the temperature range 343–503 K in mixtures of O 2 /N 2 at atmospheric pressure. Flow and static experiments have been performed in quartz and Pyrex vessels of different diameters, walls passivated or not towards reactions of radicals, and products were analyzed by GC/MS. The main products formed are butyraldehyde, hydroperoxide C 4 H 8 O 3 of MW 104, 1‐butanol, butyrolactone, and n ‐propyl hydroperoxide. It is shown that transformation of these RO radicals occurs through two reaction pathways, H shift isomerization (forming C 4 H 8 OH radicals) and decomposition. A difference of activation energies ΔE = (7.7 ± 0.1 (σ)) kcal/mol between these reactions and in favor of the H‐shift is found, leading to an isomerization rate constant k isom ( n ‐C 4 H 9 O) = 1.3 × 10 12 exp(− 9,700/RT). Oxidation, producing butyraldehyde, is proposed to occur after isomerization, in parallel with an association reaction of C 4 H 8 OH radicals with O 2 producing OOC 4 H 8 OH radicals which, after further isomerization lead to an hydroperoxide of molecular weight 104 as a main product. Butyraldehyde is mainly formed from the isomerized radical HOCCCC˙ + O 2 ··· → O (DOUBLE BOND) CCCC + HO 2 , since (i) the ratio butyraldehyde/(butyraldehyde + isomerization products) = 0.290 ± 0.035 (σ) is independent of oxygen concentration from 448 to 496 K, and (ii) the addition of small quantities of NO has no influence on butyraldehyde formation, but decreases concentration of the hydroperoxides (that of MW 104 and n ‐propyl hydroperoxide). By measuring the decay of [MW 104] in function of [NO] added (0–22.5 ppm) at 487 K, an estimation of the isomerization rate constant OOC 4 H 8 OH → HOOC 4 H 7 OH, κ 5 ≅ 10 11 exp(−17,600/RT) is made. Implications of these results for atmospheric chemistry and combustion are discussed. © 1996 John Wiley & Sons, Inc.