Preprints
https://doi.org/10.5194/egusphere-2024-3241
https://doi.org/10.5194/egusphere-2024-3241
22 Oct 2024
 | 22 Oct 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Reactivity study of 3,3-dimethylbutanal and 3,3-dimethylbutanone: Kinetic, reaction products, mechanisms and atmospheric implications

Inmaculada Aranda, Sagrario Salgado, Beatriz Cabañas, Florentina Villanueva, and Pilar Martin

Abstract. 3,3-dimethylbutanal and 3,3-dimethylbutanone are carbonyl compounds that could play a key role in tropospheric chemistry. To better understand the effects of carbonyl compounds in the atmosphere, a kinetic and mechanistic study was conducted on the degradation of 3,3-dimethylbutanal and 3,3-dimethylbutanone with atmospheric oxidants (Cl atoms, OH and NO3 radical). The kinetic experiments were performed at 710 ± 30 Torr and at room temperature (298 ± 5 K) using a relative method and FTIR (Fourier Transform Infrared Spectroscopy) to monitor the reactions. The rate coefficients (k in units of cm3 molecule-1 s-1) obtained were: kCl+33DMbutanal = (1.27 ± 0.08) × 10-10, kCl+33DMbutanone = (4.22 ± 0.27) × 10-11, and kOH+33DMbutanone = (1.25 ± 0.05) × 10-12. The reaction products were also determined using FTIR and GC-MS (Gas Chromatography/Mass Spectrometry). The main products observed were short carbonyl compounds, including acetone, formaldehyde and 2,2-dimethylpropanal. In the presence of NO, nitrated compounds are formed, and in large NO2 concentrations peroxyacetyl nitrate (PAN) and peroxy-3,3-dimethylbutyryl nitrate were clearly identified. Other unquantified compounds were multifunctional organic compounds and organic acid of low volatility. Both 33DMbutanal and 33DMbutanone degrade rapidly near emission sources with minimal impact on radiative forcing. However, they may contribute to tropospheric ozone, with a range of POCPE of 15–69, and secondary organic aerosol formation, potentially worsening air quality and contributing to photochemical smog.

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Inmaculada Aranda, Sagrario Salgado, Beatriz Cabañas, Florentina Villanueva, and Pilar Martin

Status: open (until 03 Dec 2024)

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Inmaculada Aranda, Sagrario Salgado, Beatriz Cabañas, Florentina Villanueva, and Pilar Martin
Inmaculada Aranda, Sagrario Salgado, Beatriz Cabañas, Florentina Villanueva, and Pilar Martin

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Short summary
3,3-dimethylbutanal and 3,3-dimethylbutanone are compounds that might play a big role in the chemistry of the atmosphere. To better understand their effects, the rate at which these reactions happens was measured and the reaction products were identified. The results of this study show that these compounds degrade near their sources, so they don’t have direct impact on climate. However, they can contribute to the formation of tropospheric O3 and secondary organic aerosols affecting our health.