Ozonolysis Products Research Articles

Ozonolysis of <i>α</i>-phellandrene – Part 2: Compositional analysis of secondary organic aerosol highlights the role of stabilised Criegee intermediates

Abstract. The molecular composition of the water-soluble fraction of secondary organic aerosol (SOA) generated from the ozonolysis of α-phellandrene is investigated for the first time using high-pressure liquid chromatography coupled to high-resolution quadrupole–Orbitrap tandem mass spectrometry. In total, 21 prominent products or isomeric product groups were identified using both positive and negative ionisation modes, with potential formation mechanisms discussed. The aerosol was found to be composed primarily of polyfunctional first- and second-generation species containing one or more carbonyl, acid, alcohol and hydroperoxide functionalities, with the products significantly more complex than those proposed from basic gas-phase chemistry in the companion paper (Mackenzie-Rae et al., 2017). Mass spectra show a large number of dimeric products are also formed. Both direct scavenging evidence using formic acid and indirect evidence from double bond equivalency factors suggest the dominant oligomerisation mechanism is the bimolecular reaction of stabilised Criegee intermediates (SCIs) with non-radical ozonolysis products. Saturation vapour concentration estimates suggest monomeric species cannot explain the rapid nucleation burst of fresh aerosol observed in chamber experiments; hence, dimeric species are believed to be responsible for new particle formation, with detected first- and second-generation products driving further particle growth in the system. Ultimately, identification of the major constituents and formation pathways of α-phellandrene SOA leads to a greater understanding of the atmospheric processes and implications of monoterpene emissions and SCIs, especially around eucalypt forests where α-phellandrene is primarily emitted.

Esterification for biodiesel production with a phantom catalyst: Bubble mediated reactive distillation

The initial aim of the paper is to dramatically improve the pretreatment stage of biodiesel production, which converts problematic free fatty acids to fatty acid methyl esters, by introduction of a microbubble mediated reactive distillation stage instead of acid pretreatment. This will shift the conventional esterification process towards completion with a yield higher than 80%, even without high excess methanol. Application of ozone microbubbles has the advantage over acid gas catalysis in that it gives higher conversion and leaves no catalyst residue and requires no further catalyst recovery separation steps (a “phantom” catalyst). Unreacted ozone breaks down into oxygen, so the off-gases are just a humid air stream that can be vented. Importantly, ozonolysis breaks carbon–carbon double bonds into aldehydes and carboxylic acids. Many ester species were found after contacting the feedstock with ozone-rich microbubbles, depending on the molecular structure of the alcohols for the ozonolysis of oleic acid with alcohols, i.e., methanol, ethanol, n-propanol, iso-propanol, and n-butanol. In the case of ozonolysis of used cooking oil mixed with methanol, the results from the GC–MS show that all saturated free fatty acids (including palmitic acid, stearic acid, and myristic acid) are converted to methyl esters within 20 h of 60 °C ozonolysis, whereas trace amounts of these chemicals remain at lower temperatures. The results also show that the conversion of oleic acid to form oleic acid methyl ester is 91.16% after 32 h of ozonolysis at 60 °C. Therefore, the free fatty acid content in used cooking oil is less than 1.33%, which makes it suitable as a reactant for biodiesel production via transesterification. However, this result is different from the result provided by ASTM D974 in that the acid numbers decrease dramatically by 25% at the beginning of ozonolysis followed by a plateau. Moreover, if the fluidic oscillator is used to generate bubbles in ozonolysis of oleic acid mixed with methanol, the results show that the yields of ozonolysis product 1-nonanal increase by 30%. This observation means that ozonolysis of oleic acid is relative to the specific interfacial area, and favoured at low liquid temperatures.

Multi-generation chemical aging of <i>α</i>-pinene ozonolysis products by reactions with OH

Abstract. Secondary organic aerosol (SOA) formation from volatile organic compounds (VOCs) in the atmosphere can be thought of as a succession of oxidation steps. The production of later-generation SOA via continued oxidation of the first-generation products is defined as chemical aging. This study investigates aging in the α-pinene ozonolysis system with hydroxyl radicals (OH) through smog chamber experiments. The first-generation α-pinene ozonolysis products were allowed to react further with OH formed via HONO photolysis. After an equivalent of 2–4 days of typical atmospheric oxidation conditions, homogeneous OH oxidation of the α-pinene ozonolysis products resulted in a 20–40 % net increase in the SOA for the experimental conditions used in this work. A more oxygenated product distribution was observed after aging based on the increase in aerosol atomic oxygen-to-carbon ratio (O : C) by up to 0.04. Experiments performed at intermediate relative humidity (RH) of 50 % showed no significant difference in additional SOA formation during aging compared to those performed at a low RH of less than 20 %.

Low-Temperature Ozonolysis of 2-Alkenyl-1,1-dichlorocyclopropanes

Low-temperature ozonolysis of 2-alkenyl-1,1-dichlorocyclopropanes under different conditions (O3/MeOH–CH2Cl2–NaOH, O3/MeOH or O3/CH2Cl2–AcOH with subsequent treatment with semicarbazide hydrochloride) afforded the corresponding carbonyl and carboxy derivatives at different ratios, depending on the substrate structure and workup procedure. Peroxide products of ozonolysis of 1,1-dichloro-2-ethenylcyclopropane [3-(2,2-dichlorocyclopropyl)-1,2,4-trioxolane and (2,2-dichlorocyclopropyl)(methoxy)methyl hydroperoxide] turned out to be more stable than those derived from 1,1-dichloro-2-ethenyl-2-methylcyclopropane and were isolated in the pure state.

Measurement–model comparison of stabilized Criegee intermediate and highly oxygenated molecule production in the CLOUD chamber

Abstract. Atmospheric oxidation is an important phenomenon which produces large quantities of low-volatility compounds such as sulfuric acid and oxidized organic compounds. Such species may be involved in the nucleation of particles and enhance their subsequent growth to reach the size of cloud condensation nuclei (CCN). In this study, we investigate α-pinene, the most abundant monoterpene globally, and its oxidation products formed through ozonolysis in the Cosmic Leaving OUtdoor Droplets (CLOUD) chamber at CERN (the European Organization for Nuclear Research). By scavenging hydroxyl radicals (OH) with hydrogen (H2), we were able to investigate the formation of highly oxygenated molecules (HOMs) purely driven by ozonolysis and study the oxidation of sulfur dioxide (SO2) driven by stabilized Criegee intermediates (sCIs). We measured the concentrations of HOM and sulfuric acid with a chemical ionization atmospheric-pressure interface time-of-flight (CI-APi-TOF) mass spectrometer and compared the measured concentrations with simulated concentrations calculated with a kinetic model. We found molar yields in the range of 3.5–6.5 % for HOM formation and 22–32 % for the formation of stabilized Criegee intermediates by fitting our model to the measured sulfuric acid concentrations. The simulated time evolution of the ozonolysis products was in good agreement with measured concentrations except that in some of the experiments sulfuric acid formation was faster than simulated. In those experiments the simulated and measured concentrations met when the concentration reached a plateau but the plateau was reached 20–50 min later in the simulations. The results shown here are consistent with the recently published yields for HOM formation from different laboratory experiments. Together with the sCI yields, these results help us to understand atmospheric oxidation processes better and make the reaction parameters more comprehensive for broader use.

Determining Double Bond Position in Lipids Using Online Ozonolysis Coupled to Liquid Chromatography and Ion Mobility-Mass Spectrometry.

The increasing focus on lipid metabolism has revealed a need for analytical techniques capable of structurally characterizing lipids with a high degree of specificity. Lipids can exist as any one of a large number of double bond positional isomers, which are indistinguishable by single-stage mass spectrometry alone. Ozonolysis reactions coupled to mass spectrometry have previously been demonstrated as a means for localizing double bonds in unsaturated lipids. Here we describe an online, solution-phase reactor using ozone produced via a low-pressure mercury lamp, which generates aldehyde products diagnostic of cleavage at a particular double bond position. This flow-cell device is utilized in conjunction with structurally selective ion mobility-mass spectrometry. The lamp-mediated reaction was found to be effective for multiple lipid species in both positive and negative ionization modes, and the conversion efficiency from precursor to product ions was tunable across a wide range (20-95%) by varying the flow rate through the ozonolysis device. Ion mobility separation of the ozonolysis products generated additional structural information and revealed the presence of saturated species in a complex mixture. The method presented here is simple, robust, and readily coupled to existing instrument platforms with minimal modifications necessary. For these reasons, application to standard lipidomic workflows is possible and aids in more comprehensive structural characterization of a myriad of lipid species.

One-Pot Ozonolytic Synthesis of Isoniazid Derivatives from (–)-α-Pinene and Δ3-Carene

Optically active isoniazid derivatives containing a cyclopropane or cyclobutane fragment have been synthesized by ozonolysis of (+)-Δ3-carene and (–)-α-pinene, followed by treatment of the ozonolysis products with isonicotinic acid hydrazide.

Ambient-air ozonolysis of triglycerides in aged fingerprint residues.

In forensic science, reconstructing the timing of events occurring during a criminal offense is of great importance. In some cases, the time when particular evidence was left on a crime scene is a critical matter. The ability to estimate the fingerprint age would raise the evidentiary value of fingerprints tremendously. For this purpose the most promising approach is the analysis of changes in the chemical compositions of fingerprint residues in the course of aging. The focus of our study is the identification of human specific compounds in fingerprint residues, characterized by a significant aging behavior that could analytically be used for the age determination of fingerprints in future. The first challenge is the sensitive detection of trace amounts of relevant human specific fingerprint compounds. Highly sensitive LC-MS methods were developed for the reliable structure identification of unsaturated triglycerides and their natural degradation products in order to proof the aging mechanism that takes place in fingerprint residues. Thus our results build the fundamental basis for further forensic method development and potential application in forensic investigation. Ozonolysis was found to be one of the major lipid degradation pathways in fingerprint residues in ambient air. High-resolution tandem mass spectrometry (HRMS2) was carried out to identify the ozonolysis products (TG48:0-monoozonide) formed under exposure to the highly reactive ozone in atmospheric air. The obtained products were confirmed by matrix assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI). Despite several challenges and limitations in the age estimation of fingerprints, the identification of individual degradation products of specific unsaturated lipids in aged fingerprint samples represents a significant analytical progress, resulting in a strong increase in the validity of chemical analysis of fingerprints.

Online Ozonolysis Combined with Ion Mobility-Mass Spectrometry Provides a New Platform for Lipid Isomer Analyses.

One of the most significant challenges in contemporary lipidomics lies in the separation and identification of lipid isomers that differ only in site(s) of unsaturation or geometric configuration of the carbon-carbon double bonds. While analytical separation techniques including ion mobility spectrometry (IMS) and liquid chromatography (LC) can separate isomeric lipids under appropriate conditions, conventional tandem mass spectrometry cannot provide unequivocal identification. To address this challenge, we have implemented ozone-induced dissociation (OzID) in-line with LC, IMS, and high resolution mass spectrometry. Modification of an IMS-capable quadrupole time-of-flight mass spectrometer was undertaken to allow the introduction of ozone into the high-pressure trapping ion funnel region preceding the IMS cell. This enabled the novel LC-OzID-IMS-MS configuration where ozonolysis of ionized lipids occurred rapidly (10 ms) without prior mass-selection. LC-elution time alignment combined with accurate mass and arrival time extraction of ozonolysis products facilitated correlation of precursor and product ions without mass-selection (and associated reductions in duty cycle). Unsaturated lipids across 11 classes were examined using this workflow in both positive and negative ion modalities, and in all cases, the positions of carbon-carbon double bonds were unequivocally assigned based on predictable OzID transitions. Under these conditions, geometric isomers exhibited different IMS arrival time distributions and distinct OzID product ion ratios providing a means for discrimination of cis/trans double bonds in complex lipids. The combination of OzID with multidimensional separations shows significant promise for facile profiling of unsaturation patterns within complex lipidomes including human plasma.

Transformations by Tosylhydrazide of Peroxide Ozonolysis Products of ∆3-Carene, (–)-α-Pinene, and (S)-Limonene

Tosylhydrazide was shown to be an effective reductant in protic solvents for the peroxide ozonolysis products of ∆3-carene, (–)-α-pinene, and (S)-limonene. Either α,ω-ditosylhydrazones or α,ω-ketotosylhydrazonoacids were formed depending on the nature of the trisubstituted cycloalkene.

Density Functional Theory Calculation of the Absorption Properties of Brown Carbon Chromophores Generated by Catechol Heterogeneous Ozonolysis

The effect of light-absorbing atmospheric particles on climate change has been incorporated into climate models, but the absence of brown carbon (BrC) in these models has been leading to significant differences between model predictions and measured data on radiative forcing. Also, little is known regarding the relationship between optical properties and chemical compositions of BrC. Thus, we have characterized the absorption properties of catechol and known heterogeneous ozonolysis products, with a theoretical approach based on density functional theory (DFT). While catechol presents a weak absorption maximum in the ultraviolet C (UVC) region, other polyaromatic derivatives present an absorption up to 6 times higher, with biphenyl-2,2′,3,3′-tetraol, biphenyl-3,3′,4,4′,5,5′-hexaol, and terphenyl-2′,3,3′,3″,4,4″-hexaol presenting the strongest absorption. Moreover, these derivatives now absorb in the ultraviolet B (UVB) and ultraviolet A (UVA) regions, which are types of actinic radiation in the ultraviole...

Structures of Degradation Products and Degradation Pathways of Aflatoxin B1 by High-Voltage Atmospheric Cold Plasma (HVACP) Treatment.

High-voltage atmospheric cold plasma (HVACP) is a novel nonthermal decontamination technology that has potential for use in the food industry. In this study, HVACP was applied to treat pure aflatoxin B1 (AFB1) powder on a glass slide. AFB1 was degraded by 76% using a 5 min HVACP treatment in air having 40% relative humidity. The degradation products of AFB1 were separated, and their molecular formulas were elucidated using liquid-chromatography time-of-flight mass spectrometry (HPLC-TOF-MS). Six main degradation products were observed. The structures of the degradation products were further clarified via orbitrap mass spectrometry by means of fragmentation of the parental ions. Two degradation pathways were proposed on the basis of the structure of the degradation products. Among the six degradation products, two were ozonolysis products of AFB1. The appearance of the other four degradation products indicates that AFB1 was degraded by other reactive species besides ozone that were generated during HVACP treatment. Reactive oxygen gas species are suggested as the major agents for aflatoxin degradation during HVACP treatment. Two degradation pathways of AFB1 by HVACP treatment were proposed. One pathway involves reactions in which H•, OH•, CHO• radicals are added. The other involves epoxidation by HO2• radicals and oxidation of AFB1by the combined effects of the oxidative species OH•, H2O2, and O3. According to the structure-bioactivity relationship of AFB1, the bioactivity of the AFB1 samples subjected to HVACP treatment is significantly reduced because of the disappearance of the C8═C9 double bond in the furofuran ring in all of the major degradation products as well as the modification of the lactone ring, cyclopentanone, and the methoxyl group.

The Novelties Producing by Ozonolysis of Petroleum High-Molecular Components

Specific properties of ozonolysis products of high-molecular heteroatomic compounds (resins and asphaltenes) from crude petroleums and natural bitumens are described. It is shown that polyfunctional carboxylic acids or their salts obtaining by alkaline hydrolysis of ozonization products of heavy petroleum<br />stocks permits to produce manifold useful novelties such as high-effective demulsifiers for petroleum dehydration process instead of expensive synthetic demulsifying reagents; water-soluble organic astringents suitable for chemical land-reclamation or to prepare moulding mixtures at the foundries; oily or emulsion<br />lubricating coolants for metal-working tools; stimulators of soil microorganisms activity and plant growth. The new chemical products of petroleum origin are not inferior to the best synthetic reagents for the same destinations but differ from the lasts advantageously on account of the simplicity of their production technology and low cost. The optimal expenses and other principal technological parameters were established both for raw material ozonization, following alkaline treatment and final product isolation stages of the production process for each new reagent described. By means of numerous laboratory experiments and field tests performed with seeds, bulbs and grafts of different agricultural plants and with ozonolysis products produced from the resinous components of different crude petroleums it was proved that high biological activity is characteristic only of the substances obtained from high-molecular compounds from low-sulfur naphthenic crude petroleums and natural bitumens occurring, as a rule, at small burial depths. These ozonolysis products are very effective stimulants for the different plants growth, suitable for a treatment of different forms of planting materials and providing significant acceleration of early growth stages, the reduction of vegetation and ripening periods, and the increase of total productivity of agricultural plants.

Cloud Activation Potentials for Atmospheric α-Pinene and β-Caryophyllene Ozonolysis Products.

The formation of atmospheric cloud droplets due to secondary organic aerosol (SOA) particles is important for quantifying the Earth’s radiative balance under future, possibly warmer, climates, yet is only poorly understood. While cloud activation may be parametrized using the surface tension depression that coincides with surfactant partitioning to the gas–droplet interface, the extent to which cloud activation is influenced by both the chemical structure and reactivity of the individual molecules comprising this surfactant pool is largely unknown. We report herein considerable differences in the surface tension depression of aqueous pendant droplets that contain synthetically prepared ozonolysis products derived from α-pinene and β-caryophyllene, the most abundant of the monoterpenes and sesquiterpenes, respectively, that are emitted over the planet’s vast forest ecosystems. Oxidation products derived from β-caryophyllene were found to exhibit significantly higher surface activity than those prepared from α-pinene, with the critical supersaturation required for cloud droplet activation reduced by 50% for β-caryophyllene aldehyde at 1 mM. These considerable reductions in the critical supersaturation were found to coincide with free energies of adsorption that exceed ∼25 kJ/mol, or just one hydrogen bond equivalent, depending on the ammonium sulfate and oxidation product concentration in the solution. Additional experiments showed that aldehyde-containing oxidation products exist in equilibrium with hydrated forms in aqueous solution, which may modulate their bulk solubility and surface activity. Equilibration time scales on the order of 10–5 to 10–4 s calculated for micrometer-sized aerosol particles indicate instantaneous surface tension depression in the activation processes leading to cloud formation in the atmosphere. Our findings highlight the underlying importance of molecular structure and reactivity when considering cloud condensation activity in the presence of SOA particles.

Computational Comparison of Acetate and Nitrate Chemical Ionization of Highly Oxidized Cyclohexene Ozonolysis Intermediates and Products.

During the past few years nitrate chemical ionization has been used to detect highly oxidized products from OH- and O3-initiated alkene autoxidation. These have been speculated to play a significant role in atmospheric aerosol formation. As less oxidized autoxidation products have not been detected using nitrate chemical ionization, and the absolute concentrations of the highly oxidized species are as yet unknown, other reagent ions, such as acetate, are needed both to verify the detection efficiency of nitrate chemical ionization and to measure the less oxidized compounds. Here we compare the formation free energies of the acetate and nitrate clusters of several atmospherically relevant RO2 intermediates and products derived from cyclohexene ozonolysis, calculated at the ωB97xD/aug-cc-pVTZ level of theory. We found that, for the molecules with one hydrogen bonding peroxy acid group, the binding with nitrate is on average 7.5 kcal/mol weaker than with acetate and the binding is on average 10.5 kcal/mol weaker for molecules with two hydrogen bonding peroxy acid groups. We also calculated the deprotonation energies of the RO2 intermediates and the closed-shell products and found that acetate is able to deprotonate almost all of these molecules, while deprotonation with nitrate is (as expected for the conjugate base of a strong acid) not favorable.

Intensified and safe ozonolysis of fatty acid methyl esters in liquid CO2 in a continuous reactor

We demonstrate a continuous reactor for performing the ozonolysis of fatty acid methyl esters (FAMEs) using liquid CO2 as solvent. The fast reaction kinetics allows the use of small‐volume reactors to completely convert the FAMEs, forming secondary ozonides as the primary products. The short residence times also help maximize the yields of the secondary ozonides by minimizing over‐oxidation and the formation of oligomeric products. The liquid CO2 medium promotes safe reactor operation by providing an essential fraction of overall reactor cooling and by diluting the vapor phase organics. We also demonstrate a continuous stirred reactor for the safe thermal decomposition of the secondary ozonides to their corresponding acids and aldehydes. Using a lumped kinetic model for the thermal decomposition of the ozonolysis products, we estimate activation energy values of 108.6 ± 0.6 kJ mol−1 for the decomposition of secondary ozonides and 122 ± 3 kJ mol−1 for the decomposition of the undesired oligomeric species. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2819–2826, 2017

Chemical kinetics of multiphase reactions between ozone and human skin lipids: Implications for indoor air quality and health effects.

Ozone reacts with skin lipids such as squalene, generating an array of organic compounds, some of which can act as respiratory or skin irritants. Thus, it is important to quantify and predict the formation of these products under different conditions in indoor environments. We developed the kinetic multilayer model that explicitly resolves mass transport and chemical reactions at the skin and in the gas phase (KM-SUB-Skin). It can reproduce the concentrations of ozone and organic compounds in previous measurements and new experiments. This enabled the spatial and temporal concentration profiles in the skin oil and underlying skin layers to be resolved. Upon exposure to ~30ppb ozone, the concentrations of squalene ozonolysis products in the gas phase and in the skin reach up to several ppb and on the order of ~10mmolm-3 . Depending on various factors including the number of people, room size, and air exchange rates, concentrations of ozone can decrease substantially due to reactions with skin lipids. Ozone and dicarbonyls quickly react away in the upper layers of the skin, preventing them from penetrating deeply into the skin and hence reaching the blood.

Reactions of Peroxide Products of Ozonolysis of Allyl Ethers/Esters in the АсОН-CH2Cl2 System on Treatment with Semicarbazide Hydrochloride

Background: A one-pot method for the preparation of the corresponding alkoxy acetic acids by low-temperature ozonolysis of allyl ethers/esters followed by treatment with semicarbazide hydrochloride has been suggested. The reaction occurs via formation of acetoxyhydroperoxide, subsequent reduction of which depends on the process temperature and the nature of the starting substrate. Keywords: Allyl esters, olefins, semicarbazide hydrochloride, low-temperature ozonolysis, acetoxyhydroperoxide, intermediate, alkoxy acetic acids.

Transformations of peroxide ozonolysis products of terminal olefins treated with tosylhydrazide

Transformations of peroxide ozonolysis products of terminal olefins treated with tosylhydrazide

Transformations of (–)-α-Pinene Peroxide Ozonolysis Products by Hydrazines of HCl and H2SO4

The reactivities of hydrazines of HCl and H2SO4 for (–)-α-pinene peroxide ozonolysis products were studied. It was shown that these reagents were less effective and selective than semicarbazide hydrochloride for transformations into cis-pinonic acid and its esters.