A New Mechanism for Ozonolysis of Unsaturated Organics on Solids: Phosphocholines on NaCl as A Model for Sea Salt particles

Journal Article · Mon Jan 28 04:00:00 EST 2008 · Physical Chemistry Chemical Physics. PCCP, 10(4):528-541

DOI:https://doi.org/10.1039/b712715d· OSTI ID:925712

Karagulian, Federico; Lea, Alan S; Dilbeck, Christopher W; Finlayson-Pitts, Barbara J

The ozonolysis of an approximately one monolayer film of 1-oleoyl-2-palmitoyl-sn-glycero-3-phosphocholine (OPPC) on NaCl was followed in real time using diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) at 23 °C. Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry and AUGER electron spectroscopy were used as complementary analytical techniques. Ozone concentrations ranged from 1.7 x 10¹² to 7.0 x 10¹³ molecules cm-3 (70 ppb to 2.5 ppm). Upon exposure to O3, there was a loss of C=C accompanied by the formation of a strong band at ~1110 cm-1 due to the formation of a stable secondary ozonide (1,3,4-trioxolane, SOZ). The yield of the SOZ was lower when the reaction was carried out in the presence of water vapor at concentrations corresponding to relative humidities between 2 and 25 %. The dependencies of the rate of SOZ formation on the concentrations of ozone and water vapor are consistent with the initial formation of a primary ozonide (1,2,3-trioxolane, POZ) that can react with O3 or H2O in competition with its thermal decomposition to a Criegee intermediate and aldehyde. This interpretation is also consistent with the measured dependence of the SOZ yield on the ozone concentration. Estimates were obtained for the rate constants for the POZ thermal decomposition and for its reactions with O3 and H2O, as well as for the initial reaction of O3 with OPPC. The SOZ decomposed upon photolysis at x > 300 nm, generating aldehydes, carboxylic acids and anhydrides. These studies show that the primary ozonide has a sufficiently long lifetime when formed on a solid substrate that direct reactions with O3 and H2O can compete with its thermal decomposition. In dry polluted atmospheres, ozone-alkene reactions may lead in part to the formation of stable secondary ozonides whose chemistry, photochemistry and toxicity should be taken into account in models of such regions.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 925712
• Report Number(s): PNNL-SA-56918; 12890; KP1504020
• Journal Information: Physical Chemistry Chemical Physics. PCCP, 10(4):528-541, Journal Name: Physical Chemistry Chemical Physics. PCCP, 10(4):528-541 Journal Issue: 4 Vol. 10
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALDEHYDES
ANHYDRIDES
AUGER ELECTRON SPECTROSCOPY
CARBOXYLIC ACIDS
CHEMISTRY
DIRECT REACTIONS
Environmental Molecular Sciences Laboratory
LASERS
LIFETIME
MASS SPECTROSCOPY
OZONE
PHOTOCHEMISTRY
PHOTOLYSIS
PYROLYSIS
SEAS
SPECTROSCOPY
SUBSTRATES
TOXICITY
WATER VAPOR