Kinetics and Mechanism of the Reaction of Ozone with Double Bonds

Разумовский, С. Д.; Заиков, Г. Е.

doi:10.1070/rc1980v049n12abeh002535

Cited by 55 publications

(22 citation statements)

References 6 publications

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“…It is difficult to find simple model reactions for clarification of particular properties and for the express examination of the proposed assumptions. An exception in this respect is the ozone reaction with C=C bonds, whose mechanism has been intensively studied and could be successfully applied upon ozonolysis of polymeric materials [28]. Table 2 summarizes the rate constants of the ozone reactions with some conventional elastomers and polymers and their low molecular analogues, synthesized by us.…”

Section: Resultsmentioning

confidence: 99%

Ozone and its Reactions with Diene Rubbers

Заиков¹,

Rakovsky²,

Anachkov³

2012

ChChT

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The reactions of ozone with 1,4-cispolybutadiene (SKD); Diene 35 NFA (having the following linking of the butadiene units in the rubber macromolecules: 1,4-cis (47 %), 1,4-trans (42 %), 1,2-(11 %); 1,4-cis-polyisoprene (Carom IR 2200), 1,4-trans-polychloroprene (Denka M 40), and 1,4-transpolyisoprene have been investigated in CCl 4 solutions. The changes of the viscosity of the polymer solutions during the ozonolysis have been characterized by the number of chain scissions per molecule of reacted ozone (φ). The influence of the conditions of mass-transfer of the reagents in a bubble reactor on the respective φ values has been discussed. The basic functional groups-products from the rubbers ozonolysis have been identified and quantitatively characterized by means of IR-spectroscopy and 1 H NMR spectroscopy. A reaction mechanism that explains the formation of all identified functional groups has been proposed. It has been shown that the basic route of the reaction of ozone with elastomer double bondsformation of normal ozonides-does not lead directly to a decrease in the molecular mass of the elastomer macromolecules, because the respective 1,2,4-trioxolanes are relatively stable at ambient temperature. The most favourable conditions for ozone degradation emerge when the cage interaction between Criеgee's intermediates and respective carbonyl groups does not proceed. The amounts of measured different carbonyl groups have been used as an alternative way for evaluation of the intensity and efficiency of the ozone degradation. The thermal decomposition of partially ozonized diene rubbers has been investigated by DSC. The respective values of the enthalpy, the activation energy and the reaction order of the 1, 2, 4-trioxolanes have been determined.

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Section: Resultsmentioning

confidence: 99%

Ozone and its Reactions with Diene Rubbers

Заиков¹,

Rakovsky²,

Anachkov³

2012

ChChT

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“…These results were expected because, in preliminary experiments, we noted only a partial reaction of ozone in the oil compartment, as evidenced by an increased amount of ozone recovered in a suitable iodide trap that was posed after the vessel. Such a phenomenon is justified if we consider that a substantial portion of the unsaturation became slow reacting with time, because of probabilistic and steric conditions [38]. This behavior might be due to formation of polymeric peroxides, which are responsible for viscous mass achieved after massive ozonation.…”

Section: Iodine Acid and Peroxide Valuesmentioning

confidence: 97%

Physico‐Chemical Characterization of Sesame Oil Derivatives

Zanardi

Travagli

Gabbrielli

et al. 2008

Lipids

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Ozone treatment of commercially available vegetable oils gives rise to the formation of chemical species that are responsible for the therapeutic properties of ozonated oil derivatives in dermatological diseases. In the last years, these products have been successfully used as a topical disinfectant in a number of serious skin affections. The medical application of empirically prepared ozonated oil has yielded striking improvements with unexpected and rapid healing, compelling us to begin a long-range study aiming first to define the main characteristics of the most common ozonated vegetable oils, about which there is usually no medical consensus because of the lack of standardization of their technological parameters. Sesame oil was selected because of its great amount of polyunsaturated acyl groups, as well as natural antioxidants. Moreover, we have determined the kinetics and optimal conditions of ozonation (e.g., ozone concentrations, time of exposure, temperature) for obtaining an ozonated oil characterized by well-established technological and physico-chemical properties, namely an accurate peroxide value determination. On the basis of the results, we have gained an understanding of the modifications of the vegetable oils during the ozonation process.

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“…9À12, 22 The reactor volume was reduced to 2 mL to determine the minimum needed. Using the standard conditions, no decene was detected by GC when using a 2-mL reactor (entry 5, Table 3).…”

Section: Articlementioning

confidence: 99%

Ozonolysis in Flow Using Capillary Reactors

Roydhouse

Ghaini

Constantinou

et al. 2011

Org. Process Res. Dev.

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Reactions of n-decene with ozone and subsequent quenching of the formed ozonides were carried out under flow conditions using the standard Vapourtec flow system equipped with a cooled flow cell. The reactions were performed continuously and in the annular flow regime within the circular cross-section channels. Typical flow rates were 0.25À1 mL min À1 for liquid and 25À100 mL min À1 for gas, reactor volumes were 0.07À10 mL formed of 1 mm ID PFA tubing. The reaction temperature was À10°C. The flow was not always smooth, while waves in the liquid film and droplets in the gas core were observed. Liquid residence times were found to be independent of gas flow rates and increasing with decreasing liquid flow rates. Substrate residence times in the ozonolysis reactor ranged between 1 and 80 s, and complete conversion could be achieved at ∼1 s residence time. Two common reductants, triethylphosphite and triphenylphosphine, were examined as to their suitability under flow conditions. Triphenylphosphine achieved faster reduction of the intermediate ozonides, resulting in a greater than 10:1 selectivity for the aldehyde over the corresponding acid. The cooling system provided a safe and efficient control of the highly exothermic reaction system. The configuration of the system allowed the production of chemically significant amounts (1.8 g h À1 at 1.3 ozone equivalents), with minimal amounts of ozonides present at any time. ' INTRODUCTIONOzone is an oxidant that has been used for decades in organic synthesis 1 and in the purification/deodorisation of water. 2 Ozonolysis is the addition of ozone to a substance, resulting initially in a primary ozonide which then usually rearranges to a more stable secondary ozonide in the case of alkenes. 3 The most common substrates for ozonolysis are unsaturated species containing either double or triple carbonÀcarbon bonds, which result usually in aldehydes/ketones and acids. This transformation has great utility in synthesis both in a research and an industrial setting. Ozone can also be used to oxidise phosphorus 1,4 and sulphur 1,5 compounds as well as organometallics 6 and other inorganic species. 6 The advantages of using ozone over other oxidants is the low cost and toxicity of the byproduct, i.e. DMSO from DMS, Ph 3 PO from PPh 3 as compared with high oxidation level metallic oxidants, e.g. chromium. Some of the drawbacks of using ozone at scale are the high exotherms associated with the initial reaction of substrates with ozone. 7 Also the intermediate ozonides are unstable (although some can be isolated at room temperature) and are an explosion risk due to the instability of the OÀO single bond; the build-up of these materials must be avoided. The use of continuous flow can alleviate both the exotherm problem and the build-up of potentially explosive materials (if suitable reagents are used to quench them in flow).Microreactors have shown several benefits in the past years. Microstructured devices provide short diffusion pathways, improved heat and mass transfer rates, and increa...

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Kinetics and Mechanism of the Reaction of Ozone with Double Bonds

Cited by 55 publications

References 6 publications

Ozone and its Reactions with Diene Rubbers

Ozone and its Reactions with Diene Rubbers

Physico‐Chemical Characterization of Sesame Oil Derivatives

Ozonolysis in Flow Using Capillary Reactors

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