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Temperature Dependence of Aqueous-Phase Decomposition of α-Hydroxyalkyl-Hydroperoxides.
- Source :
-
The journal of physical chemistry. A [J Phys Chem A] 2020 Dec 10; Vol. 124 (49), pp. 10288-10295. Date of Electronic Publication: 2020 Nov 24. - Publication Year :
- 2020
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Abstract
- Ozonolysis of unsaturated organic species with water produces α-hydroxyalkyl-hydroperoxides (α-HHs), which are reactive intermediates that lead to the formation of H <subscript>2</subscript> O <subscript>2</subscript> and multifunctionalized species in atmospheric condensed phases. Here, we report temperature-dependent rate coefficients ( k ) for the aqueous-phase decomposition of α-terpineol α-HHs at 283-318 K and terpinen-4-ol α-HHs at 313-328 K. The temporal profiles of α-HH signals, detected as chloride adducts by negative-ion electrospray mass spectrometry, showed single-exponential decay, and the derived first-order k for α-HH decomposition increased as temperature increased, e.g., k (288 K) = (4.7 ± 0.2) × 10 <superscript>-5</superscript> , k (298 K) = (1.5 ± 0.4) × 10 <superscript>-4</superscript> , k (308 K) = (3.4 ± 0.9) × 10 <superscript>-4</superscript> , k (318 K) = (1.0 ± 0.2) × 10 <superscript>-3</superscript> s <superscript>-1</superscript> for α-terpineol α-HHs at pH 6.1. Arrhenius plot analysis yielded activation energies of 17.9 ± 0.7 (pH 6.1) and 17.1 ± 0.2 kcal mol <superscript>-1</superscript> (pH 6.2) for the decomposition of α-terpineol and terpinen-4-ol α-HHs, respectively. Activation energies of 18.6 ± 0.2 and 19.2 ± 0.5 kcal mol <superscript>-1</superscript> were also obtained for the decomposition of α-terpineol α-HHs in acidified water at pH 5.3 and 4.5, respectively. Theoretical kinetic and thermodynamic calculations confirmed that both water-catalyzed and proton-catalyzed mechanisms play important roles in the decomposition of these α-HHs. The relatively strong temperature dependence of k suggests that the lifetime of these α-HHs in aqueous phases (e.g., aqueous aerosols, fog, cloud droplets, wet films) is controlled not only by the water content and pH but also by the temperature of these media.
Details
- Language :
- English
- ISSN :
- 1520-5215
- Volume :
- 124
- Issue :
- 49
- Database :
- MEDLINE
- Journal :
- The journal of physical chemistry. A
- Publication Type :
- Academic Journal
- Accession number :
- 33231452
- Full Text :
- https://doi.org/10.1021/acs.jpca.0c09862