Autoxidation products

Hydroxyalkyl peroxyesters also have been isolated from the autoxidation products of aldehydes and by esterification of hydroxyhydroperoxides (44). 

The Pacman catalyst selectively oxidized a broad range of organic substrates including sulfides to the corresponding sulfoxides and olefins to epoxides and ketones. However, cyclohexene gave a typical autoxidation product distribution yielding the allylic oxidation products 2-cyclohexene-l-ol (12%) and 2-cyclohexene-1-one (73%) and the epoxide with 15% yield [115]. 

This autoxidation product of 1,1,2,3-tetrachloro-l,3-butadiene exploded during attempted vacuum distillation. 

W.E. Neff, W.C. Byrdwell, Characterization of model triacylglycerol (triolein, trilinolein and trilinolenin) autoxidation products via high performance liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry, Journal of Chromatography A, 818, 169 186 (1998). 

Slight SH, Prabhakaram M, Shin DB, Feather MS and Ortwerth BJ (1992) The extent of N-(carboxymethyl)lysine formation in lens proteins and polylysine by the autoxidation products of ascorbic acid. Biochim Biophys Acta 1117, 199-206. 

The kinetic results are summarized in Table II. The autoxidation products in general are similar to those observed by Van Sickle at lower temperatures and conversions. Table III summarizes analyses made by Van Sickle at conditions approximating our levels of conversion and temperature. The polymeric dialkyl peroxides are included in the residue. 

Figure 7. First derivative ESR spectra of radical anions observed in dimethyl sulfoxide solutions of potassium tert-butoxide. Top, autoxidation product of diphenylamine. No signal was observed in the absence of oxygen. Middle, autoxidation of 4-hydroxy-diphenylamine. Bottom, spontaneous reduction product of mono-anil of p-benzoquinone.

Method E from X -phosphorins over autoxidation products. 

The parent heterocycles (Table 13) display a strong band near 220 nm with one additional band at longer wavelengths for thiophene and selenophene, and two for tellurophene. Analogous weak bands reported in the older literature for furan and pyrrole are now generally accepted as arising from autoxidation products. 

The solution spectrum of pyrrole displays a strong band at ca. 210 nm (Table 23). The weak band at ca. 240 nm reported in the older literature is now generally accepted as arising from autoxidation products. Substitution of methyl for hydrogen generally leads to... 

The polymeric pyrrolic autoxidation products probably result from the oxidized monomeric systems, which are analogous in structure to those isolated from photooxidation and peroxide oxidation reactions. Thus, for example, analysis of the products of the autoxidation of 1-methylpyrrole (Scheme 47) would suggest that 1 -methyl-A3-pyrrolin-2-one (153) is initially formed from a radical reaction of the pyrrole with triplet oxygen. This reaction sequence should be compared with that proposed for the oxidation of pyrroles with hydrogen peroxide (Scheme 50), which yields (181), (182) and (183) as the major isolable products. The acid-catalyzed reaction of a pyrrole with its oxidation product e.g. 153) also results in the formation of polymeric material and the formation of pyrrole black is probably a combination of oxidation and acid-catalyzed polymerization processes. 

Because autoxidation products of linoleic acid would confound the results, it is preferable to isolate linoleic acid by either TLC, HPLC, or silicic acid column chromatography before using it in the reaction. 

Viinanen and Hopia (145) described an evaporative light-scattering detector (ELSD) that can be used to detect autoxidation products of TAG standards [trilinolenin (TLn), trilinolein (TL), and triolein (TO)] and of a natural mixture of rapeseed oil (RSO) TAGs. The samples were oxidized at 40°C in the dark in open 10-ml test tubes. Sample aliquots of 500 mg were taken for... 

Comparison of the two different types of detector, UV and ELSD, showed that the chromatographic profiles of the autoxidized samples are similar except for TO. Compounds without conjugated dienes in their structure cannot be detected with a UV detector at 235 nm thus, the autoxidation products of TO are not detected. The detection limit of ELSD was 150 ng, quantified by 1,3-diolein and 2-monolinolein, and its sensitivity in detecting autoxidation products of TLn and TL approached that of the UV detector used in the study. The two detectors could therefore be used in series. 

S Kato, K Kanohta. Chromatographic studies of the autoxidation products of ethoxyquin and its photochemical conversion. J Chromatogr 324 462-468, 1985. 

The [Ru(P)]2 systems are extremely air-sensitive (see Sect. 3.22). The first sample alleged to be [Ru(OEP)]2 [32] was probably one of its autoxidation products, [RuOH(OEP)]20 (see Sect. 3.22). A molecular thin film claimed to contain porphyrin dimers prepared from RuCO(Meso-IX-DME)Py by irradiation [221] showed UV/Vis spectra similar to those described for the first such product [32]. Therefore, it probably contained also a p-oxobis(ruthenium(IV)) complex. 

In the case of the API dihydroergocristine methanesulfonate, autoxi-dation of the olefin moiety yields the corresponding autoxidation products (Fig. 102) (146). 

V-Formylkynurenine is one of the 16 autoxidation products of tryptophan (51) (Fig. 8). The dye-sensitized photo-oxygenation of tryptophan in sodium carbonate - acetic acid buffer (pH 7) gave TV-for my Iky n urenine as the major product (52). This is also the oxidation product of tryptophan with hydrogen peroxide (53) and with ozone (54). This is an interesting case the same degradation impurity can be obtained in different ways, probably... 

Spontaneous oxidation of amines by one-electron transfer has been reported as a key process in polar solvents (35). It is not easy to distinguish the spontaneous and initiated mechanisms, because these pathways have a common intermediate (XI, Fig. 9). Thus, potassium hexacyanoferrate (III), a one-electron oxidant, gives electron transfer oxidation of amines (56) yielding the classical radical autoxidation products. 

Raftery DP, Smyth MR, Leonard RG, Kneafsey BJ, Brennan MC. Identification of hydrogen peroxide as the autoxidation product of N-phenyl-2-propyl-3,5-diethyl-l,2-dihydropiridine. Anal Commun 1996 33 375-379. 

Oyler AR, Naldi RE, Facchine KL, Burinsky DJ, Cozine MH, Dunphy R, Alves-Santana JD, Cotter ML. Characterization of autoxidation products of... 

Also identified in this system are 2-alkylfurans. 2-Alkylfur-ans are known thermal and autoxidation products of unsaturated fatty acids (23). 2-Alkylfurans identified in this study are presumably derived by the thermal oxidation of 2,4-decadienal. 

Reactions of Metal Complexes Directly with Substrate and Autoxidation Products. 303... 

In addition to the usual reactions of the catalyst with intermediate hydroperoxides, the second type of reaction undoubtedly involves direct reaction of the metal catalyst with the hydrocarbon substrate and/or with secondary autoxidation products. Two possible pathways can be visualized for the production of radicals via direct interaction of metal oxidants with hydrocarbon substrates, namely, electrophilic substitution and electron transfer. Both processes are depicted below for the reaction of a metal triacetate with a hydrocarbon. 

These two processes are used as a basis for the discussion of various examples of redox reactions between metal complexes and hydrocarbon substrates, or secondary autoxidation products, in the following. 

Esters of the fatty acid oleic acid are components of membranes that are subject to autoxidation. Explain which hydrogens of an oleate ester you expect to be abstracted most readily by a radical. Show the structures of the major autoxidation products that would be formed from an oleate ester. 

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