Ozonolysis Of Alkenes Research Articles

Peroxide Intermediates of Olefin Ozonolysis—Carbonyl Oxides: Kinetics of Reactions

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Ozonolysis and photolysis of alkene-terminated self-assembled monolayers on quartz nanoparticles: implications for photochemical aging of organic aerosol particles

Photolysis of alkene-terminated self assembled monolayers (SAM) deposited on Degussa SiO(2) nanoparticles is studied following oxidation of SAM with a gaseous ozone/oxygen mixture. Infrared cavity ring-down spectroscopy is used to observe gas-phase products generated during ozonolysis and subsequent photolysis of SAM in real time. Reactions taking place during ozonolysis transform alkene-terminated SAM into a photochemically active state capable of photolysis in the tropospheric actinic window (lambda > 295 nm). Formaldehyde and formic acid are the observed photolysis products. Photodissociation action spectra of oxidized SAM and the observed pattern of gas-phase products are consistent with the well-established Criegee mechanism of ozonolysis of terminal alkenes. There is strong evidence for the presence of secondary ozonides (1,3,4-trioxalones) and other peroxides on the oxidized SAM surface. The data imply that photolysis plays a role in atmospheric aging of primary and secondary organic aerosol particles.

Aldehyde and Ketone Functions Further Substituted on Oxygen

AbstractFor Abstract see ChemInform Abstract in Full Text.

Photochemical Sources of Organic Acids. 2. Formation of C5−C9 Carboxylic Acids from Alkene Ozonolysis under Dry and Humid Conditions

The dependence of organic acid generation by alkene ozonolysis on relative humidity, thermalized Criegee intermediate scavengers, and alkene structure is investigated. Carboxylic acids generated from the ozonolysis of 1-hexene, 1-octene, 1-decene, trans-3-octene, and 1-methylcyclohexene were analyzed as trimethylsilyl (TMS) derivatives. Experiments were performed under dry (relative humidity (RH) < 1%) and humid (RH = 65%) conditions with cyclohexane or n-butyl ether as an OH scavenger. Pentanoic acid is produced from 1-hexene and trans-3-octene with yields 8.5 +/- 2.6 and 5.0 +/- 1.5% under dry conditions and 5.1 +/- 1.5 and 2.8 +/- 0.8% under humid conditions, respectively. Heptanoic acid yields from 1-octene are 8.3 +/- 2.5 and 4.4 +/- 1.3% under dry and humid conditions, respectively. Ozonolysis of 1-methylcyclohexene produced six C5-C7 multifunctional carboxylic acids, with a total yield of 7%. Several other acids and aldehydes were also monitored and quantified. An additional set of experiments with added stabilized Criegee intermediate (SCI) scavengers was performed for 1-octene ozonolysis under dry conditions. The results indicate that SCIs and their reaction with water are minor contributors to acid formation in the atmosphere and suggest that many of the acids are formed directly.

Photochemical Sources of Organic Acids. 1. Reaction of Ozone with Isoprene, Propene, and 2-Butenes under Dry and Humid Conditions Using SPME

Formation of C4 and smaller carboxylic acids from gas-phase ozonolysis of several alkenes under dry (relative humidity (RH) < 1%) and humid (RH = 65%) conditions have been investigated. We have developed a technique based on solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) to quantify the acids, as well as other products, and applied it to the reactions of ozone with propene, trans-2-butene, 2,3-dimethyl-2-butene, and isoprene. Acetic acid yields from propene and trans-2-butene ozonolysis in the presence of an OH scavenger were 2.7 +/- 0.6 and 2.9 +/- 0.6%, respectively, under dry conditions and 1.8 +/- 0.4 and 2.3 +/- 0.5% at 65% RH. Isoprene ozonolysis produced methacrylic and propenoic acids with yields of 5.5 +/- 1 and 3.0 +/- 1%, under dry conditions and 4.1 +/- 1 and 1.5 +/- 0.3% under wet conditions, respectively. That water inhibits acid formation indicates that the water reaction with stabilized Criegee intermediates is at most a minor source of acids. Acids that may form as coproducts of the OH radical elimination pathway, acetic acid from 2,3-dimethylbutene and isoprene, and propenoic acid from isoprene were also observed with significant yields (up to 10%), although the production of acetic acid was not a linear function of the alkene reacted. Carbonyl products are also reported.

Ozonolysis of Alkenes and Study of Reactions of Polyfunctional Compounds: LXVII. Synthesis of 27,27,27-Trifluoro-20-hydroxyecdysone Acetonides from 24,25- and 25,26-Anhydro-20-hydroxyecdysone Derivatives via Ozonolysis and Trifluoromethylation

Ozonolysis of 24,25/25,26-anhydro derivatives of 20-hydroxy-2,3:20,22-di-O-isopropylidene-ecdysone and 2,3-di-O-acetyl-20-hydroxy-20,22-O-isopropylideneecdysone, followed by trifluoromethylation of the corresponding 25-oxo derivatives afforded 2,3:20,22-di-O-isopropylidene- and 20,22-O-isopropylidene-27,27, 27-trifluoro-20-hydroxyecdysones.

Quantum Chemical and Master Equation Simulations of the Oxidation and Isomerization of Vinoxy Radicals

The vinoxy radical, a common intermediate in gas-phase alkene ozonolysis, reacts with O2 to form a chemically activated alpha-oxoperoxy species. We report CBS-QB3 energetics for O2 addition to the parent (*CH2CHO, 1a), 1-methylvinoxy (*CH2COCH3, 1b), and 2-methylvinoxy (CH3*CHCHO, 1c) radicals. CBS-QB3 predictions for peroxy radical formation agree with experimental data, while the G2 method systematically overestimates peroxy radical stability. RRKM/master equation simulations based on CBS-QB3 data are used to estimate the competition between prompt isomerization and thermalization for the peroxy radicals derived from 1a, 1b, and 1c. The lowest energy isomerization pathway for radicals 4a and 4c (derived from 1a and 1c, respectively) is a 1,4-shift of the acyl hydrogen requiring 19-20 kcal/mol. The resulting hydroperoxyacyl radical decomposes quantitatively to form *OH. The lowest energy isomerization pathway for radical 4b (derived from 1b) is a 1,5-shift of a methyl hydrogen requiring 26 kcal/mol. About 25% of 4a, but only approximately 5% of 4c, isomerizes promptly at 1 atm pressure. Isomerization of 4b is negligible at all pressures studied.

Dibromomethane as one-carbon source in organic synthesis: total synthesis of (±)- and (−)-methylenolactocin

A general method was developed to construct monocyclic α-methylene-γ-butyrolactone moiety. The key step is to introduce the α-methylene group by the ozonolysis of mono-substituted alkenes followed by reacting with a preheated mixture of CH 2Br 2–Et 2NH. Application of this key step in the total synthesis of the (±)- and (−)-methylenolactocin was described.

Unusual aggregates from the oxidation of alkene self-assembled monolayers: a previously unrecognized mechanism for SAM ozonolysis?

Self-assembled monolayers (SAMs) of vinyl-terminated 3- and 8-carbon compounds were generated on Si substrates and reacted at room temperature with approximately 1 ppm gaseous O(3). A combination of atomic force microscopy (AFM), scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to study the surface composition and morphology after oxidation. A distribution of large ( approximately 0.1-10 microm) organic aggregates was formed, while the surrounding substrate became depleted of carbon compared to the unreacted SAM. This highly unusual result establishes that the mechanism of ozonolysis of alkene SAMs must have a channel that is unique compared to that in the gas phase or in solution, and may involve polymerization induced by the Criegee intermediate (CI). Oxidation at 60% RH led to the formation of a number of smaller aggregates, suggesting water intercepted the CI in competition with aggregate formation. The uptake of water, measured using transmission FTIR, was not increased upon oxidation of these films. In conjunction with literature reports of polymer formation from VOC-NO(x) photooxidations, these results suggest that formation of aggregates and polymers in the atmosphere is much more widespread than previously thought. The implications for the ozonolysis of alkenes on surfaces, for the transformation of organics in the atmosphere, and for the reactions and stability of unsaturated SAMs, are discussed.

Complete ozonolysis of alkyl substituted ethenes at −60 °C: distributions of ozonide and oligomeric products

The distribution of ozonide and oligomeric structures formed on complete ozonolysis of alkenes in a non-participating solvent at -60 degrees C is governed by the alkyl substitution around the carbon-carbon double bond. The ozonolysis of a 1,1-alkyl substituted ethene generally favours the formation of an ozonide (a 1,2,4-trioxolane). Whereas the ozonolysis of a 1,1,2-alkyl substituted ethene also produces ozonide, a considerable amount of the ozonised products are oligomeric in nature. For example, the ozonolysis of 3-methylpent-2-ene in solution to high conversion in pentane yields oligomers with structural units derived from the fragmentation products of the primary ozonide (a 1,2,3-trioxolane) which are namely butanone carbonyl oxide and acetaldehyde; these can be characterised by electrospray ionisation mass spectroscopy (ESI-MS) under soft ionisation conditions. The predominant oligomers formed are rich in carbonyl oxide units (80 + mol%) and are cyclic in nature. A small proportion of the oligomers formed are open chain compounds with end groups that suggest that chain termination is brought about either by water or by hydrogen peroxide. Residual water in the solvent will react with the carbonyl oxides to produce 2-methoxybut-2-yl hydroperoxide, which we propose readily decomposes generating hydrogen peroxide. A significant yield of oligomers also is obtained from the ozonolysis of a 1,2-alkyl substituted ethene. The ozonolysis of trans-hex-2-ene in pentane yields oligomers containing up to four structural units and are predicted to be mainly cyclic.

Cycloalkene ozonolysis: collisionally mediated mechanistic branching.

Master equation calculations on a computational potential energy surface reveal that collisional stabilization at atmospheric pressure becomes important in the gas-phase ozonolysis of endocyclic alkenes for a carbon number between 8 and 15. Because the reaction products from endocyclic ozonolysis are tethered, this system is ideal for consideration of collisional energy transfer, as chemical activation is confined to a single reaction product. Collisional stabilization of the Criegee intermediate precedes collisional stabilization of the primary ozonide by roughly an order of magnitude in pressure. The stabilization of the Criegee intermediate leads to a dramatic transformation in the dominant oxidation pathway from a radical-forming process at low carbon number to a secondary ozonide-forming process at high carbon number. Secondary ozonide formation is important even for syn-isomer Criegee intermediates, contrary to previous speculation. We use substituted cyclohexenes as analogues for atmospherically important mono- and sesquiterpenes, which are major precursors for secondary organic aerosol formation in the atmosphere. Combining these calculations with literature experimental data, we conclude that the transformation from chemically activated to collisionally stabilized behavior most probably occurs between the mono- and sesquiterpenes, thus causing dramatically different atmospheric behavior.

Dibromomethane as One‐Carbon Source in Organic Synthesis: A Versatile Methodology to Prepare the Cyclic and Acyclic α‐Methylene or α‐Keto Acid Derivatives from the Corresponding Terminal Alkenes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Der Mechanismus der Alken‐Ozonolyse – eine kritische Betrachtung

AbstractThe Mechanism of Alkene Ozonolysis – a Critical Examination. Alkene ozonolyses have been carried out in experimental organic chemistry for more than a century, and a lucid description of the underlying reaction mechanism has been developped and integrated in most chemistry textbooks. Nevertheless, there are a great number of exceptions hard to rationalize by the accepted mechanism. Attempts in the past to give more‐convincing answers to this problem failed. Therefore, the search for an alternative mechanistic model without contradictions is compelling. The present paper offers a redox model based upon the known properties of ozone both as a strong oxidant and an O‐atom‐transferring agent, especially when reacted with alkenes of sufficiently high electron density to act as reducing partners.

Ozonolyse von Enolethern. 10. Mitteilung

AbstractOzonolysis of Enol Ethers. Part 10. Ozonization of Enol Ethers from 1,2‐ and 1,3‐Dicarbonyl Compounds: Direct Quantitative Synthesis of Phthalonic Acid Anhydride The results of ozonolyses of enol ethers from 1,2‐ and 1,3‐dicarbonyl compounds presented here strongly indicate that these reactions do not proceed via the established Criegee ozonolysis mechanism for nucleophilic CC bonds. The quantitative one‐step synthesis of phthalonic acid anhydride via ozonolysis of 2‐(methoxymethyliden)‐1H‐inden‐1,3(2H)‐dione (28a) is described. Furthermore, a revision of the theory of alkene ozonolysis in the presence of tetracyanoethylene (TCNE) is proposed on the basis of a single‐electron‐transfer (SET) chemistry.

Secondary Organic Aerosol Formation from the Ozonolysis of Cycloalkenes and Related Compounds

The secondary organic aerosol (SOA) yields from the laboratory chamber ozonolysis of a series of cycloalkenes and related compounds are reported. The aim of this work is to investigate the effect of the structure of the hydrocarbon parent molecule on SOA formation for a homologous set of compounds. Aspects of the compound structures that are varied include the number of carbon atoms present in the cycloalkene ring (C5 to C8), the presence and location of methyl groups, and the presence of an exocyclic or endocyclic double bond. The specific compounds considered here are cyclopentene, cyclohexene, cycloheptene, cyclooctene, 1-methyl-1-cyclopentene, 1-methyl-1-cyclohexene, 1-methyl-1-cycloheptene, 3-methyl-1-cyclohexene, and methylenecyclohexane. The SOA yield is found to be a function of the number of carbons present in the cycloalkene ring, with an increasing number resulting in increased yield. The yield is enhanced by the presence of a methyl group located at a double-bonded site but reduced by the presence of a methyl group at a non-double-bonded site. The presence of an exocyclic double bond also leads to a reduced yield relative to that of the equivalent methylated cycloalkene. On the basis of these observations, the SOA yield for terpinolene relative to the other cyclic alkenes is qualitatively predicted, and this prediction compares well to measurements of the SOA yield from the ozonolysis of terpinolene. This work shows that relative SOA yields from ozonolysis of cyclic alkenes can be qualitatively predicted from properties of the parent hydrocarbons.

Secondary organic aerosol formation from cyclohexene ozonolysis: effect of OH scavenger and the role of radical chemistry.

To isolate secondary organic aerosol (SOA) formation in ozone-alkene systems from the additional influence of hydroxyl (OH) radicals formed in the gas-phase ozone-alkene reaction, OH scavengers are employed. The detailed chemistry associated with three different scavengers (cyclohexane, 2-butanol, and CO) is studied in relation to the effects of the scavengers on observed SOA yields in the ozone-cyclohexene system. Our results confirm those of Docherty and Ziemann that the OH scavenger plays a role in SOA formation in alkene ozonolysis. The extent and direction of this influence are shown to be dependent on the specific alkene. The main influence of the scavenger arises from its independent production of HO2 radicals, with CO producing the most HO2, 2-butanol an intermediate amount, and cyclohexane the least. This work provides evidence for the central role of acylperoxy radicals in SOA formation from the ozonolysis of alkenes and generally underscores the importance of gas-phase radical chemistry beyond the initial ozone-alkene reaction.

Dibromomethane as one-carbon source in organic synthesis: a versatile methodology to prepare the cyclic and acyclic α-methylene or α-keto acid derivatives from the corresponding terminal alkenes

Ozonolysis of mono-substituted alkenes A- 1 followed by reacting with a preheated mixture of CH 2Br 2–Et 2NH affords α-substituted acroleins A- 2 in good yields. Under very mild reaction conditions, these α-substituted acroleins A- 2 can be easily converted to α-methylene esters A- 4 , which could be further converted to the corresponding α-keto esters A- 5 . This methodology can be also applied to the preparation of α-methylene lactones B- 4 , α-methylene lactams, and α-keto lactones B- 5 with various ring sizes.

Atmospheric particle formation from the ozonolysis of alkenes in the presence of SO2

Abstract Laboratory studies on the formation of new particles have been performed in a flow tube in the system O 3 /alkene/SO 2 using α -pinene, trans -butene, and tetramethylethylene (TME) as model alkenes. Reactant concentrations were kept close to atmospheric conditions. In the absence of SO 2 , no particle formation was observed. The number of newly formed particles measured in the presence of SO 2 was found to be H 2 SO 4 -controlled, whereas a distinct contribution of different organic products from the ozonolysis was not discovered. Scavenger experiments for OH radicals revealed that the main fraction of H 2 SO 4 produced arose from OH+SO 2 . An additional pathway for H 2 SO 4 , probably Criegee Intermediate+SO 2 , accounted for 26% ( α -pinene), 23% ( trans -butene), and 42% (TME) of the total amount of H 2 SO 4 formed. For conditions where particle formation occurred in the flow tube, H 2 SO 4 concentrations of a few 10 7 molecule cm −3 were calculated, similar to observations in the atmosphere. Under the experimental conditions used, an analysis of the particle volume indicated that the organic ozonolysis products did not influence the particle growth significantly.

Computational Studies of the Chemistry of Syn Acetaldehyde Oxide

Syn carbonyl oxides generated in alkene ozonolysis have been implicated as sources of hydroxy radical (•OH) in the atmosphere. We report quantum chemical calculations at the B3LYP/6-31G(d,p), CBS-QB3, MPW1K/6-31+G(d,p), and CBS-APNO levels to characterize the reactivity of syn acetaldehyde oxide and its vinyl hydroperoxide isomer. The vinoxy radical formed upon vinyl hydroperoxide decomposition is converted to a chemically activated peroxy radical in the presence of O2. All methods besides MPW1K predict that this species undergoes a 1,4-hydrogen shift with an activation barrier of ∼20 kcal/mol and then decomposes to yield •OH. RRKM/Master equation calculations predict that this unimolecular reaction of the peroxy radical will compete significantly with its collisional stabilization even up to 1 atm pressure. This chemistry can partly account for the •OD radicals recently observed in the ozonolysis of alkenes with vinylic deuteriums. The CBS-QB3 and CBS-APNO methods predict relative energies that agree to ...

Reaction of Criegee Intermediates with Water VaporAn Additional Source of OH Radicals in Alkene Ozonolysis?

The yields of OH radicals from the ozonolysis of ethene and trans-2-butene under dry and humid conditions (0% and 65% relative humidity, respectively) were measured by the small-ratio relative rate technique. The OH yields from both alkenes are found to be independent of the humidity within the error limits of the experiments. This suggests that the OH yield from the reaction of Criegee intermediates with water is less than 30%. These findings are supported by Master equation calculations that are consistent with the major product from the reaction of Criegee intermediates with water being the hydroxyalkyl hydroperoxide (RCH(OH)OOH), with a smaller contribution from OH. Implications of these results for both the fundamental reaction mechanism of ozone-alkene reactions and the fate of Criegee intermediates in the troposphere are discussed.