65424-60-4Relevant academic research and scientific papers
Thermal stability of carbonyl radicals. Part I. Straight-chain and branched C4 and C5 acyl radicals
Jagiella,Libuda,Zabel
, p. 1175 - 1181 (2007/10/03)
The competition between thermal decomposition (k(dis)) and O2 addition (k(O2)) of linear and branched C4 and C5 alkanoyl (R-C(.)O, R = alkyl) radicals has been studied in a photochemical reaction chamber made from stainless steel (v = 12 L). RCO radicals were prepared by continuous photolysis of Br2-RC(O)H-O2-NO2-N2 mixtures at wavelengths ≥420 nm. The products CO and RC(O)O2NO2 were analyzed by long-path IR absorption using an FT-IR spectrometer. Rate constant ratios k(dis)/k(O2) were determined at 317 K for n-butyryl, n-pentanoyl, 3-methylbutyryl, 2-methylpropionyl and 2- methylbutyryl and at 6 temperatures between 293 and 317 K for 2,2- dimethylpropionyl (=pivaloyl, t-butyl-CO) radicals. Total pressures were 1 bar (M = N2 + O2). Adopting the literature value of k(O2) for acetyl, unimolecular decomposition rate constants k(dis) were derived from the measured ratios k(dis)/k(O2). k(dis) at 298 K, 1 bar, M = O2 + N2 increases by factors of 35, 54 and 24 for each H atom in CH3CO which is consecutively replaced by a methyl group (corresponding to increasing branching of R). For the unimolecular decomposition of 2,2-dimethylpropionyl radicals, the Arrhenius expression k(dis)(t-butyl-CO) = 6.0 x 1012 exp(- 41.6 kJ mol-1/RT) s-1 (2σ) was derived for the temperature range 293-317 K and a total pressure of 1 bar (M = N2 + O2). The results on k(dis)/k(O2) show that even for the thermally most unstable of the carbonyl radicals studied in this work, i.e. 2,2-dimethylpropionyl, only 1.8% decompose rather than add O2 at 298 K and 1 bar in dry air.
Peroxyisobutyryl nitrate
Grosjean,Grosjean,Williams II
, p. 167 - 172 (2007/10/03)
Peroxyisobutyryl nitrate, (CH3)2CHC(O)OONO2(PiBN), has been synthesized in the liquid phase, measured by electron capture gas chromatography (EC- GC), characterized in a number of decomposition tests, and prepared in-situ in the gas phase by sunlight irradiation of isobutyl nitrite, of isobutanal with NO, and of 3-methyl-1-butene with NO in air. The corresponding reaction mechanisms are outlined. In the liquid phase, PiBN decomposes to isopropyl nitrate. In the gas phase, thermal decomposition in the presence of NO yields acetone (91 ± 7%). Isobutanal reacts with OH predominantly (≥98%) by H abstraction from the carbonyl carbon, and 3-methyl-1-butene reacts with OH predominantly (≥98%) by addition on the C=C bond. Reaction with oxygen predominates (≥96%) over unimolecular decomposition for the alkoxy radicals (CH3)2CH(O) and (CH3)2CHCH2(O). Emission inventory data for hydrocarbons that are precursors to PiBN indicate that the PiBN-forming potential relative to that of PAN is ≤0.10. This ratio also represents an upper limit for the positive bias due to PiBN when measuring ambient PAN by EC-GC with packed columns, on which PiBN and PAN co-elute.
