Quantification of hydroxycarbonyls from OH-isoprene reactions.
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Hydroxycarbonyls arising from OH-initiated reactions of isoprene have been quantified by the technique of a flow reactor coupled to proton-transfer reaction mass spectrometry (PTR-MS) detection. The yields of C5- and C4-hydroxycarbonyls are (19.3 +/- 6.1)% and (3.3 +/- 1.6)%, respectively, measured at a flow tube pressure of about 100 Torr and at a temperature of 298 +/- 2 K. A yield of (8.4 +/- 2.4)% is obtained for the unsaturated carbonyl C5H8O, confirming that internal OH addition represents the minor channel in the initial OH-isoprene reaction. The results show that those carbonyl compounds account for the most previously unquantified carbon, enabling the isoprene carbon closure. The study also reveals novel aspects of the delta-hydroxyalkoxy radical degradation mechanism, which is essential for modeling tropospheric O3 formation. In addition, this work demonstrates the application of PTR-MS for quantification of products of hydrocarbon reactions, which should have profound impacts on elucidation of the chemistry of atmospheric anthropogenic and biogenic hydrocarbons.
author list (cited authors)
Zhao, J., Zhang, R., Fortner, E. C., & North, S. W.