Papers by Malene Bech Sørensen
The Journal of Physical Chemistry A, 2003
The kinetics and products of the OH-and NO 2-initiated oxidation of 2,4-hexadiene have been inves... more The kinetics and products of the OH-and NO 2-initiated oxidation of 2,4-hexadiene have been investigated at 296 K and 700 Torr by long-path Fourier transform infrared (FTIR) spectroscopy. Relative rate methods were employed for the photolysis of 2,4-hexadiene/CH 3 ONO/NO/air mixtures to measure k(OH + 2,4-hexadiene)) (1.76 (0.58) × 10-10 cm 3 molecule-1 s-1. The OH-initiated oxidation of 2,4-hexadiene gave acetaldehyde, trans-crotonaldehyde, and 2,5-dimethylfuran, with molar yields of (30.6 (5.0)%, (12.9 (2.0)%, and (5.6 (1.0)%, respectively. These products suggest that the OH-initiated oxidation of 2,4hexadiene proceeds, at least partially, by pathways analogous to those reported for 1,3-butadiene and isoprene. From the pseudo-first-order decay of 2,4-hexadiene in the presence of excess NO 2 , a value of k(NO 2 + 2,4hexadiene)) (3.11 (0.18) × 10-19 cm 3 molecule-1 s-1 was derived. The reaction stoichiometry and products were investigated in the absence of O 2 , in the presence of O 2 , and in the presence of O 2 and NO. Reaction mechanisms consistent with the observations are presented. In the presence of NO and O 2 , the NO 2-initiated chemistry leads to NO-to-NO 2 conversion, and the formation of HO x radicals in significant yield, such that 2,4-hexadiene removal occurs by reaction with both NO 2 and OH. The results are consistent with HO x yields of up to 0.75 (0.05, depending on the experimental conditions. The results also suggest that the nitrate forming channels account for (25 (5)% of the reactions of NO with peroxy radicals formed from the reactions of both OH and NO 2 with 2,4-hexadiene. The implications of the results are discussed within the context of the atmospheric chemistry of conjugated dienes. As part of this work, rate coefficients were determined for the reactions of NO 2 with 1,3-butadiene and styrene and for NO with 2,4-hexadiene: k(NO 2 + 1,3-butadiene)) (2.54 (0.15) × 10-20 , k(NO 2 + styrene)) (1.4 (0.3) × 10-20 , and k(NO + 2,4-hexadiene) e 2 × 10-21 cm 3 molecule-1 s-1 .
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Papers by Malene Bech Sørensen