Preprints
https://doi.org/10.5194/acp-2017-163
https://doi.org/10.5194/acp-2017-163
12 Apr 2017
 | 12 Apr 2017
Status: this preprint was under review for the journal ACP but the revision was not accepted.

Experimental and computational kinetics investigations for the reactions of Cl atoms with series of unsaturated ketones in gas phase

Siripina Vijayakumar, Avinash Kumar, and Balla Rajakuma

Abstract. Temperature dependent rate coefficients for the gas phase reactions of Cl atoms with 4-hexen-3-one and 5-hexen-2-one were measured over the temperature range of 298–363 K relative to 1-pentene, 1,3-butadiene and isoprene. Gas Chromatography (GC) was used to measure the concentrations of the organics. The derived temperature dependent Arrhenius expressions are k4-hexen-3-one+Cl (298–363 K) = (2.82 ± 1.76)×10−12exp [(1556 ± 438)/T] cm3 molecule−1 s−1 and k5-hexen-2-one+Cl (298–363 K) = (4.6 ± 2.4)×10−11exp[(646 ± 171)/T] cm3 molecule−1 s−1. The corresponding room temperature rate coefficients are (5.54 ± 0.41)×10−10 cm3 molecule−1 s−1 and (4.00 ± 0.37)×10−10 cm3 molecule−1 s−1 for the reactions of Cl atoms with 4-hexen-3-one and 5-hexen-2-one respectively. To understand the mechanism of Cl atom reactions with unsaturated ketones, computational calculations were performed for the reactions of Cl atoms with 4-hexen-3-one, 5-hexen-2-one and 3-penten-2-one over the temperature range of 275–400 K using Canonical Variational Transition state theory (CVT) with Small Curvature Tunneling (SCT) in combination with CCSD(T)/6-31+G(d, p)//MP2/6-311++G(d, p) level of theory. Atmospheric implications, reaction mechanism and feasibility of the title reactions are discussed in this manuscript.

Siripina Vijayakumar, Avinash Kumar, and Balla Rajakuma
Siripina Vijayakumar, Avinash Kumar, and Balla Rajakuma
Siripina Vijayakumar, Avinash Kumar, and Balla Rajakuma

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Short summary
we report the experimentally measured rate coefficients. Theoretically explored all the possible channels and computed the rate coefficients. The estimated atmospheric lifetimes of these unsaturated ketones due to their reactions with atmospheric oxidants are presented. These kinetic parameters will be helpful to understand the atmospheric degradation of unsaturated ketones in the troposphere. Also, the degradation mechanism of these ketones due to their oxidation with Cl atoms is proposed.
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