Peroxide, formation from ethanes

However, there are also very important limitations. As we mentioned above, even in oxidation of methane and ethane many elementary reactions are not accessible for direct and detailed investigation. When we shift from ethane to propane, not only the number of carbon atoms in the molecule increases, but also the complexity of the reaction network. In particular, one may assume that even in propane oxidation the formation of complex oxygenate intermediates, including bi-radicals and complex peroxides, may take place. Although such compounds can play a principal role in kinetically relevant steps (such as chain-branching), up to now our knowledge about such compounds is negligible. 

Figure 8, Influence of dimethylamine on formation of methane and ethane from tert-butyl peroxide at 153°C.

Perhydroxyl radical, 75 thermal generation from PNA of, 75 Peroxy radical generation, 75 Peroxide crystal photoinitiated reactions, 310 acetyl benzoyl peroxide (ABP), 311 radical pairs in, 311, 313 stress generated in, 313 diundecanyl peroxide (UP), 313 derivatives of, 317 EPR reaction scheme for, 313 IR reaction scheme for, 316 zero field splitting of, 313 Peorxyacetyl nitrate (PAN), 71, 96 CH3C(0)00 radical from, 96 ethane oxidation formation of, 96 IR spectroscopy detection of, 71, 96 perhydroxyl radical formation of, 96 synthesis of, 97 Peroxyalkyl nitrates, 83 IR absorption spectra of, 83 preparation of, 85 Peroxymethyl reactions, 82 Photochemical mechanisms in crystals, 283 atomic trajectories in, 283 Beer s law and, 294 bimolecular processes in, 291 concepts of, 283... 

Fig. 18. Product formation during the oxidation of propane in the absence of pic d arret. Initial temperature = 430 °C initial pressure of propane = 60 torr initial pressure of oxygen = 240 torr. (b) Left ordinate +, methyl alcohol. Right ordinate X, isopropyl alcohol , ethyl alcohol o, n-propyl alcohol , allyl alcohol (xO.5). (c) Left ordinate +, hydrogen peroxide , formaldehyde. Right ordinate x, total aldehydes, (d) +, propene , methane , ethylene x, ethane. (From ref. 147.) References pp. 361—367...

One approach to determination of whole-body lipid peroxidation has been measurement of exhaled hydrocarbons by GLC, especially ethane. Hydrocarbon gases are, however, minor end-products of peroxidation and their formation depends on the decomposition of peroxide. Recent studies have demonstrated that isoprostane is a good biomarker of lipid peroxidation in the human body. Isoprostanes are specific products arising from the peroxidation of unsaturated fatty acid residues in lipids and detection of them and their metabolites in urine is a useful assay of whole-body lipid peroxidation. Isoprostanes can be accurately and sensitively measured by mass spec-trometric techniques. 

Benzocyclopropene reacts with a variety of radical reagents (for example A -bromosuccinimide carbon tetrachloride bromotrichloromethane bromoform/benzoyl peroxide alkyl sulfide and ethane-1,2-dithiol with photolysis) to afford products derived from cleavage of the cyclopropane ring. The preferential mode of reaction consists of a chain reaction initiated by radical addition at Cl a followed by opening of the cyclopropyl radical to afford a benzyl radical. Yields are generally low except for the addition of the alkylsulfanyl radical, e.g. formation of 1, and no products derived from addition to the central tt-bond are formed. Cyclopropa[A]naphthalene reacts similarly with radicals and gives 2-methylnapthalene derivatives, while no addition to the central 7i-bond is observed. ... 

It has been hypothesized on the basis of the formation of trichlo-roacetate from aliphatic compounds, especially acetate, by the action of chloroperoxidase in the presence of hydrogen peroxide and chloride that this might be a naturally occurring metabolite (Haiber et al. 1996). Plausible mechanisms for the formation of trichloroacetic acid by atmospheric reactions involving trichloro-ethane and tetrachloroethene are discussed in Section 4.1.2. 

The peroxidative reactions were mediated and sustained by Cu(II) ions in the light. Table IV shows that fatty acids with at least 2 double bonds are necessary for hydrocarbon formation. As Anacystis lacks those fatty acids, no peroxidative volatile hydrocarbons were produced. Spirulina exclusively contains CO-6 fatty acids as endogenous polyunsaturated fatty acids and evolved Cs hydrocarbons only. The third species, Anabaena, whose thylakoids contain co-3 and Co-6 polyunsaturated fatty acids formed C2 and C5 hydrocarbons simultaneously. We conclude that co-3 polyunsaturated fatty acids are the source of ethane and ethylene and that the CO-6 polyunsaturated fatty acids are the source of pentane and pentene in herbicide-induced peroxidation reactions. Furthermore, we obtained evidence that the propane measured with Bumilleriopsis after an 18-h treatment with either 10 >iM oxyfluorfen or 50 jxM Cu(II) originates from a CO-4 polyunsaturated fatty acid. We have recently isolated and identified this acid as 16 3CO4 (Sandmann, Lambert, B5ger in preparation). 

During lipid peroxidation, n-3 fatty acids decompose to produce ethane, whereas -6 fatty acids produce pentane, which can be detected in exhaled breath. A higher breath pentane formation rate therefore indicates more peroxidation of 71-6 fatty acids. Breath pentane and plasma vitamin E levels were measured in 10 normal subjects, and in 5 patients receiving parenteral nutrition diets who wwe deficient in vitamin E. Half of die normal subjects then received 1000 lU of, , , -a-tocopheryl acetate for 10 days, and breath pentane and plasma vitamin E levels were re-measured. Data taken from Lemoyne et al. (1987). lU, international units of, , i -a-tocopherol equivalents. 

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