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1.
Previous studies of secondary oxidation products by high-pressure liquid chromatography (HPLC) of autoxidized methyl oleate,
linoleate and linolenate and photosensitized-oxidized linoleate are extended to photosensitized-oxidized linolenate. Photosensitized-oxidized
linolenate was fractionated by silicic acid chromatography with diethyl ether/hexane mixtures. Selected silicic acid chromatographic
fractions were separated by polar phase HPLC and characterized by thin layer and gas liquid chromatography and by ultraviolet,
infrared, nuclear magnetic resonance and mass spectrometry. Secondary products from the photosensitized oxidation mixtures
(containing 8.2 to 29.0% monohydroperoxides) included keto- and epoxy-dienes (0.4–1.6%), hydroperoxy epidioxides (0.8–4.9%),
hydroperoxy bicyclic monoenes (0.1–0.3%), dihydroperoxides (1.0–5.6%), and hydroperoxy bisepidioxides (0.7–1.6%). Some of
these secondary products are new and unique to photosensitized oxidation. Cyclization of the 10-, 12-, 13- and 15-hydroperoxides
of linolenate would account for their lower relative concentration than that found for the 9- and 16-hydroperoxides. Dihydroperoxides
may be derived from monohydroperoxides by singlet oxygenation or free radical oxidation. The hydroperoxy bis-epidioxides may
be formed by further serial cyclization of the hydroperoxy epidioxides from 10- and 15-monohydroperoxides. Dihydroperoxides,
hydroperoxy epidioxides and hydroperoxy bis-epidioxides are suggested as important flavor precursors in oxidized fats.
The mention of firm names or trade products does not imply that they are endorsed by the US Department of Agriculture over
other firms or similar products not mentioned. 相似文献
2.
A previous study of autoxidation products by high pressure liquid chromatography (HPLC) of methyl oleate and linoleate was
extended to methyl linolenate. Autoxidized methyl linolenate was fractionated by HPLC either after reduction to allylic alcohols
on a reverse phase system, or directly on a micro silica column. Isolated oxidation products were characterized by thin layer
and gas liquid chromatography and by ultraviolet, infrared, nuclear magnetic resonance and mass spectrometry. Secondary products
from the autoxidation mixtures (containing 3.5–8.5% monohydroperoxides) included epoxy unsaturated compounds (0.2–0.3%), hydroxy
or hydroperoxy-cyclic peroxides (3.8–7.7%), epoxy-hydroxy dienes (<0.1%), dihydroxy or dihydroperoxides with conjugated diene-triene
and conjugated triene systems (0.9–2.9%). Cyclization of the 12- and 13-hydroperoxides of linolenate would account for their
lower relative concentration than the 9- and 16-hydroperoxides. Dihydroperoxides may be derived from the 9- and 16-linolenate
hydroperoxides. Cyclic peroxides and dihydroperoxides are suggested as important flavor precursors in oxidized fats. 相似文献
3.
A high-performance liquid chromatographic method, using post-column detection with diphenyl-1-pyrenyl-phosphine (DPPP), was
developed for the quantitative and qualitative determination of isomeric lipid hydroperoxides (OOH). The OOH eluted from a
normal-phase column were passed through a photodiode array detector and then mixed with DPPP solution in a reaction coil heated
at 80°C. DPPP oxide formed by the reaction with OOH was determined by monitoring the fluorescence intensity at 380 nm and
excitation at 352 nm. The conjugated diene OOH (13-cis, trans- and 9-cis, trans-OOH) and nonconjugated OOH (12-cis-trans- and 10-cis, trans-OOH) from photosensitized oxidation of methyl linoleate were determined in a molar ratio of 31∶29∶19∶21, respectively. However,
only the two conjugated hydroperoxides were detected by ultraviolet absorption at 234 nm. Further applications were carried
out for the determination of OOH of methyl oleate and methyl linolenate. This method proved to be useful for the determination
of the OOH containing both conjugated and nonconjugated diene structures. 相似文献
4.
The hydroperoxides in oxidized mixtures of methyl oleate, linoleate and linolenate were analyzed by reducing the hydroperoxides
to the corresponding hydroxyesters and separating the hydroxyesters from the unoxidized esters by thin layer chromatography
(TLC). The hydroxyesters from linolenate were separated from the other hydroxyesters by TLC on silver ion plates. The hydroxyesters
were converted to TMS-hydroxy derivatives. The TMS-hydroxyoleate and TMS-hydroxylinoleate were separated by gas chromatography
(GC), and all the TMS-derivatives were quantified by GC. The relative rates of oxidation of methyl oleate, linoleate and linolenate
in mixtures were ca. 1∶10.3∶21.6. The hydroperoxides formed in the oxidation of soybean and olive oils were similar before
and after randomization and similar to corresponding methyl ester mixtures.
Journal Paper No. J-9657 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project 2143. 相似文献
5.
Henry W. -S. Chan 《Journal of the American Oil Chemists' Society》1977,54(3):100-104
The photo-sensitized oxidation of methyl linolenate and methyl oleate was studied using erythrosine and riboflavin as sensitizers.
The complex mixtures of hydroperoxides obtained were analyzed for the proportion of conjugated products and, after reduction
to the corresponding mixtures of hydroxystearates, for the distribution of positional isomers. By comparing the mixtures with
that obtained from autoxidation, it was shown that the riboflavin reaction involved the “Type 1” mechanism of photosensitized
oxidation which proceded via the formation of diene-radicals and yielded the same positional isomers of hydroperoxides as
autoxidation. Thus, mixtures of the 8, 9, 10, and 11 positional isomers of allylic hydroperoxides were formed from oleate
and the 9, 12, 13, and 16 isomers of conjugated diene-hydroperoxides from linolenate oxidation. The erythrosine reaction,
on the other hand, proceded via the “Type 2”. mechanism which involved singlet oxygen as the oxygenating species. The mixtures
of isomers resulting from oxidation involving singlet oxygen were different from those obtained by autoxidation. Oleate oxidation
gave rise to a mixture of only the 9 and 10 positional isomers while the mixture obtained from oxidation of methyl linolenate
contained non-conjugated hydroperoxide isomers (with the hydroperoxide group at positions 10 and 15) as well as the conjugated—9,
12, 13, and 16—isomers. 相似文献
6.
The proportion of geometrical hydroperoxide isomers generated by aerobic oxidation of methyl linoleate (18∶2 Me) in either
aqueous emulsion consisting of Tris-HCl buffer (pH 7.4) or in a homogeneous dichloromethane solution was determined to understand
the mechanism of lipid oxidation in different reaction systems. Four geometrical isomers were generated after oxidation of
18∶2 Me in dichloromethane: methyl 13-hydroperoxy-cis-9,trans-11-octadecadienoate, methyl 13-hydroperoxy-trans-9,trans-11-octadecadienoate, methyl 9-hydroperoxy-trans-10,cis-12-octadecadienoate, and methyl 9-hydroperoxy-trans-10,trans-12-octadecadienoate in the ratios of 1∶4∶1∶4, respectively. The ratios between each isomer did not change until the peroxide
value (PV) increased to 58 meq/kg. Oxidation of 18∶2 Me in aqueous emulsion yielded the same geometrical isomers of hydroperoxide.
However, the ratios were different: 3∶2∶3∶2 until the PV increased to 110 meq/kg. Predominant (60%) formation of trans,trans hydroperoxide isomers was obtained in the oxidation of a mixture of 18∶2 Me and methyl laurate (12∶0 Me). These results are
interpreted to reflect the importance of the concentration of hydrogen atom-donating equivalents to the kinetic preference
for different products. The high effective concentration of hydrogen donors in the oxidation of 18∶2 Me in emulsions favored
the formation of the less stable cis,trans isomers. The lower concentration of hydrogen donor in the dichloromethane solution effectively slowed hydrogen donation and
led to the strong preference for the more stable trans,trans isomers. This interpretation was further tested by preparing emulsions of 18∶2 Me and 12∶0 Me to dilute concentration of
hydrogen-donating species using the nonhydrogen-donating 12∶0 Me. Consistent with the proposed hypothesis, the proportion
of trans,trans isomers increased as a result of 12∶0 Me addition. 相似文献
7.
Carolyn B. Kenaston Karl M. Wilbur Athos Ottolenghi Frederick Bernheim 《Journal of the American Oil Chemists' Society》1955,32(1):33-35
Summary The thiobarbituric acid (TBA) reaction for fatty acid oxidation has been compared with Lundberg and Chipault's method for
peroxides, the Kreis test for aldehydes, and with the degree of conjugation, using fatty acid esters exposed to ultraviolet
light for various periods. The TBA test paralleled the other methods for methyl linolenate and methyl linoleate but was essentially
negative for methyl oleate oxidation.
The sensitivity of the TBA test for linolenate was 30–80 times that for linoleate at the same peroxide values. The TBA test
appears to be a reliable method of estimating the oxidation products of linolenic and linoleic acids in tissues and other
biological material.
Supported by a grant from the Atomic Energy Commission. 相似文献
8.
The role of singlet oxygen in oxidation was studied by analyzing hydroperoxide isomers in unsaturated fats and esters by gas
chromatography-mass spectrometry (GC-MS). On oxidation photosensitized with methylene blue at 0 C, methyl oleate produced
a 50–50% mixture of 9- and 10-hydroperoxides, linoleate a mixture of 66% conjugated (9+13) and 34% unconjugated (10+12) hydroperoxides,
and linolenate a mixture of 75% conjugated (9+12+13+16) and 25% unconjugated (10+15) hydroperoxides. Cottonseed, safflower,
and corn oil esters showed, as in soybean esters, the presence of varying amounts of 12-hydroxy esters derived from the corresponding
hydroperoxide at low peroxide values. Since these oils do not contain linolenic acid, a likely source of the 12-hydroperoxide
is linoleic acid by photosensitized oxidation. Several lines of evidence support the conclusion that singlet oxygen may contribute
to the unique hydroperoxide composition of vegetable oil esters at low levels of oxidation. In the presence of photosensitizers
such as methylene blue and chlorophyll, the unique hydroperoxide composition (high levels of 10- and 12-hydroperoxides) obtained
in soybean esters was similar to that produced by oxidation at low peroxide values. In contrast, a normal hydroperoxide composition
was produced, as expected from the fatty acid composition of soybean oil esters, when singlet oxygen quenchers such as β-carotene
and α-tocopherol were used and when the esters were treated with carbon black to remove natural photosensitizers. GC-MS analyses
of the derived unsaturated alcohols provided indirect evidence for 12-hydroperoxy-9,13-diene in soybean esters as expected
by photosensitized oxidation of linoleate.
Presented at the AOCS Meeting, San Francisco, California, April 29–May 3, 1979.
The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of
Agriculture over other firms or similar products not mentioned. 相似文献
9.
E. N. Frankel W. E. Neff W. K. Rohwedder B. P. S. Khambay R. F. Garwood B. C. L. Weedon 《Lipids》1977,12(12):1055-1061
The gas chromatography-mass spectrometry (GC-MS) method developed in the preceding papers was extended to the analysis of
autoxidation products of methyl linolenate. Four isomeric hydroxy allylic trienes with a conjugated diene system were identified
after reduction of the linolenate hydroperoxides. All eight geometrictrans,cis- andtrans, trans-conjugated diene isomers of these hydroxy allylic compounds were identified and partially separated by GC of the trimethylsilyl
(TMS) ether derivatives. The proportion found of 9- and 16-hydroperoxides was significantly higher (75–81%) than the 12- and
13-hydroperoxides (18–25%). The tendency of the 12- and 13-hydroperoxides to form cyclic peroxides, cyclic peroxidehydroperoxides,
and prostaglandin-like endoperoxides was supported by indirect evidence for the presence of 9,10,12- and 13,15,16-trihydroxyoctadecanoate
in hydrogenated derivatives of the highly oxygenated products. The quantitative GC-MS method was used to determine the relative
contribution of linolenate, linoleate, and oleate in mixtures to the formation of hydroperoxides.
Presented at the AOCS Meeting, New York, May 1977. 相似文献
10.
Carter Litchfield Raymond Reiser A. F. Isbell G. L. Feldman 《Journal of the American Oil Chemists' Society》1964,41(1):52-55
Three nitrile silicone polymers have been evaluated as liquid phases for gas chromatographic separation of the geometric isomers
of methyl oleate, methyl linoleate, and methyl linolenate on capillary columns. A polymer of β-cyanoethylmethylsiloxane proved
the most effective. This liquid phase separated oleate from elaidate, resolved the four geometric isomers of linoleate into
three peaks, and divided the eight geometric isomers of linolenate into six peaks. Two other copolymers of dimethylsiloxane
and β-cyanoethylmethylsiloxane gave poorer resolution ofcis-trans isomers, but showed different elution patterns for the geometric isomers of linoleate and linolenate.
Presented at the AOCS meeting, Atlanta, Ga., 1963. 相似文献
11.
Autoxidation of polyunsaturated triacylglycerols. IV. Volatile decomposition products from triacylglycerols containing linoleate and linolenate 总被引:4,自引:0,他引:4
Trilinoleoylglycerol (LLL), trilinolenoylglycerol (LnLnLn) and four synthetic triacylglycerols were autoxidized and the volatile
products were investigated to determine the effect of fatty acid glyceride position on the mechanism of hydroperoxide decomposition.
Capillary gas chromatography provided a sensitive method to follow the volatile oxidation products of mixtures of LLL and
LnLnLn and of synthetic triacylglycerols containing linoleate and linolenate in different known positions. The relative amount
of linoleate oxidation was determined by analyzing for hexanal, 2-heptenal and 2,4-decadienal, and the relative amount of
linolenate oxidation by analyzing for 2,4-heptadienal and 2,4,7-decatrienal. The volatiles from pure monohydroperoxides of
LLL and LnLnLn were compared with those of the corresponding triacylglycerols by capillary gas chromatography. Significant
differences in the distribution of volatile products were observed depending on the triacylglycerols precursor. A 1∶1 mixture
of LLL and LnLnLn autoxidized at 40°C showed an equal contribution of linolenate and linoleate volatiles at a peroxide value
of 34. The synthetic triacylglycerols LLnL and LLLn (L, linoleic; Ln, linolenic acid) formed initially about the same total
volatiles, whereas LnLnL formed more volatiles than LnLLn. The ratio Ln to L volatile products was the same for the diL triacylglycerols,
and higher for LnLnL than for LnLLn. This new information should permit us to better understand the influence of triacylglycerol
structure on the relative oxidative stability of unsaturated triacylglycerols.
Presented in part at the 80th Annual American Oil Chemists' Meeting, Cincinnati, OH, May 3–6, 1989. 相似文献
12.
To clarify the sources of undesirable flavors, pure hydroperoxides from autoxidized and photosensitized oxidized fatty esters
were thermally decomposed in the injector port of a gas chromatograph-mass spectrometer system. Major volatile products were
identified from the hydroperoxides of methyl oleate, linoleate and linolenate. Although the hydroperoxides from autoxidized
esters are isomerically different in position and concentration than those from photosensitized oxidized esters, the same
major volatile products were formed but in different relative amounts. Distinguishing volatiles were, however, produced from
each type of hydroperoxide. The 9- and 10-hydroperoxides of photosensitized oxidized methyl oleate were thermally isomerized
in the injector port into a mixture of 8-, 9-, 10- and 11-hydroperoxides similar to that of autoxidized methyl oleate. Under
the same conditions, the hydroperoxides from autoxidized linoleate and linolenate did not undergo significant interconversion
with those from the corresponding photosensitized oxidized esters. The compositions of the major volatile decomposition products
are explained by the classical scheme involving carboncarbon scission on either side of alkoxy radical intermediates. Secondary
reactions of hydroperoxides are also postulated, and the hydroperoxy cyclic peroxides from methyl linoleate (photosensitized
oxidized) and methyl linolenate (both autoxidized and photosensitized oxidized) are suggested as important precursors of volatiles. 相似文献
13.
Cholesteryl stearate, oleate, linoleate, linolenate and arachidonate were oxidized in solid form (at 100 C) and in a water
dispersion (in the presence of potassium stearate, pH 7.5, 80 C). The unsaponifiable fraction was analyzed by capillary gas
liquid chromatography. In the solid state, the oxidation rates of esterified cholesterol were high for stearate and oleate,
low for the polyunsaturated esters and very low for free cholesterol. In water dispersion, the rates were reversed, e.g.,
free cholesterol oxidized more quickly than its stearic and oleic acid esters. The fatty chains in 18∶0 and 18∶1 inhibited
the autoxidation of cholesterol. Hydroxylation of the cholesterol side chain only occurred during solid-state autoxidation
as previously observed by others. The 20- and 25-hydroxycholesterols were never detected in the products of micellar reactions,
regardless of which surfactant was used for micelle formation. 相似文献
14.
Linalyl oleate (LO), an interesterification product of linalyl acetate (LA) and methyl oleate catalyzed with sodium methoxide,
was studied to determine its effectiveness in retarding oxidative changes in soybean oil heated continuously at 180±5°C for
32 h. The identity of LO was established by GC-MS and NMR. LO was tested at levels of 0.05 and 0.1% and compared with the
more commonly used synthetic autoxidation inhibitor methyl silicone (MS) at levels of 5 and 10 ppm. FA changes and conjugated
dienoic acid formation were monitored. First-order kinetic equations were used to model the decreases in linoleate (18∶2)/palmitate
and linolenate (18∶3)/palmitate ratios. Plots of the data show an inflection point at ∼11 h. Oils with either level of MS
and LO had lower reaction rate constants before the inflection points, and lower conjugated diene values and higher 18∶2 and
18∶3 percentages at the end of the 32-h heating period than did oil without additives and with LA. LO could replace methyl
silicone in soybean oil during deep-fat frying but at levels about 100 times greater. [We propose to use the term “autoxidation
inhibitor” for substances that inhibit autoxidation when added to fats and oils at low concentrations and whose mechanism
of action may be unknown. Some may wish to call such substances “antioxidants” but others wish to reserve this term for substances
that end free radical chains by hydrogen radical donation. Some refer to methyl silicone as a “polymerization inhibitor”,
but this term suggests more about its mechanism of action than seems warranted.] 相似文献
15.
Phenyl linoleate was oxidized under different conditions. The monohydroperoxide products were isolated and subsequently hydrogenated.
The isomers of phenyl hydroxysterate obtained were separated by high pressure liquid chromatography. On the basis of cochromatography
with reference materials and mass spectroscopy, it was shown that the mixture was composed mainly (96%) of phenyl 9-hydroxy-
and phenyl 13-hydroxysterates (9- and 13-HOPh) with 8-, 10-, 12- and 14-HOPh as minor compounds (4%). In the minor fraction,
the 8- and 14-HOPh predominated in comparison to the 10- and 12-HOPh. The presence of α-tocopherol in the autoxidation experiment
changed the proportion of the phenyl hydroxystearate isomers: the proportion of the 9- and 13-HOPh increased and those of
the 8- and 14-HOPh decreased. After addition of 0.05% or higher concentrations of α-tocopherol, the minor fraction comprised
approximately equal amounts of 8-, 10-, 12- and 14-HOPh. Autoxidation of phenyl oleate followed by hydrogenation of the monohydroperoxides
resulted in the formation of a mixture of phenyl hydroxystearates containing approximately equal amounts of 8-, 9-, 10- and
11-HOPh.
Presented at the 74th annual meeting of the American Oil Chemists' Society in Chicago, May 1983. 相似文献
16.
The rate of addition of hydrogen sulfide to high purity methyl oleate, methyl linoleate, methyl linolenate, methyl 9,11-trans,trans-octade-cadienoate and methyl β-eleostearate was investigated at 25 C with UV irradiation. A similar study was carried out
with soybean, linseed and tung oils in the absence and presence of 2,2′-azo-bis(isobutyronitrile) with UV photolysis. Initially
the reaction of hydrogen sulfide with methyl esters appears to follow pseudo-zero-order kinetics although as the reaction
proceeds the kinetics of the polyunsaturated ester reactions become more complex. For nonconjugated systems the overall rate
is determined by the initiation step, whereas the overall rate of addition to conjugated systems is a function of the stability
of the resonance-stabilized addition radical in the chain transfer step. For methyl esters the following order of reactivity
appears to hold:
Methyl oleate ≅ methyl linoleate ≅ methyl linolenate >> methyl 9,11-trans,trans-octadecadienoate > methyl β-eleostearate. Using 2,2′-azo-bis(isobutyronitrile) with UV photolysis markedly increases the
rate of addition of hydrogen sulfide to nonconjugated vegetable oils.
Presented at the AOCS Meeting, New York, October 1968.
No. Utiliz. Res. Dev. Div., ARS, USDA. 相似文献
17.
Marcel S. F. Lie Ken Jie C. C. Lam Mohammed Khysar Pasha 《Journal of the American Oil Chemists' Society》1996,73(5):557-562
13C nuclear magnetic resonance (NMR) spectroscopic analysis of the whole oil (triacylglycerols) ofBiota orientalis seeds confirms the presence of oleate [18:1(9Z)], linoleate [18:2(9Z, 12Z)], linolenate [18:3((9Z, 12Z, 15Z)], 20:3 (5Z,
11Z, 14Z), 20:4(5Z, 11Z, 14Z, 17Z), and saturated fatty acids in the acyl groups by comparing the observed carbon shifts with
previously established shift data for model triacylglycerols. This technique shows that the saturated, 20:3 and 20:4 fatty
acids are distributed mainly in the α-acyl positions, whereas oleate, linoleate, and linolenate are randomly acylated to the
α- and β-positions of the glycerol “backbone”. Stereospecific hydrolysis of theBiota oil with pancreatic lipase, followed by chromatographic analysis of fatty esters, reveals the presence of trace amounts of 16:0(0.7%),
18:0(0.5%), 20:3 (0.4%), and 20:4 (1.3%) in the β-position of the glycerol “backbone”, which are undetectable by13C NMR technique on the whole oil. Semiquantitative assessment of the13C NMR signal intensities gives the relative percentages of the fatty acid distribution as: saturated 16:0, 18:0 (12.0% α-acyl),
oleate (7.7% α-acyl 8.7% β-acyl), total linoleate and linolenate (31.7% α-acyl; 24.2% βacyl), total 20:3 and 20:4 (15.7% α-acyl).
The13C NMR spectroscopic analysis of carrot seed oil identifies the presence of saturated (18:0), 18:1(6Z), 18:1(9Z), and 18:2(9Z,
12Z). The saturated fatty acid is found in the α-acyl positions. Semi-quantitative assessment of the signal intensities gives
the relative percentages of the fatty acids as: 18:0 (4.5% α-acyl), 18:1(6Z) (49.6% α-acyl; 19.7% β-acyl), oleate (6.5% α-acyl;
8.6% β-acyl) and linoleate (5.2% α-acyl; 6.9% β-acyl). 相似文献
18.
Sprecher H 《Lipids》1968,3(1):14-20
Methyl 4-decenoate (10∶1ω6), methyl dodeca-3,6-dienoate (12∶2ω6), methyl tetradeca-5,8-dienoate (14∶2ω6) and methyl hexadeca-7,10-dienoate
(16∶2ω6) were prepared by total synthesis. Rats raised on a fat-deficient diet for 2 1/2 months received 100 mg per day of
one of the experimental acids or methyl linoleate for a period of 16 days. The liver lipids were extracted, converted to methyl
esters and analyzed by gas-liquid chromatography. Neither 10∶1ω6 nor 12∶2ω6 served as biosynthetic precursors for linoleate.
Small amounts of 14∶2ω6 were convered to linoleate while 16∶2ω6 served as an efficient precursor for linoleate and longer
chain ω6 acids. None of the short chain ω6 acids were incorporated directly into liver lipids. 相似文献
19.
Dietary deficiency of essential fatty acids of the n−3 and n−6 series is known to promote a compensatory increase in polyenoic
fatty acids of the n−9 series in the lipids of mammalian tissues. In the present study long-chain n−9 polyenes were found
to be normal components of the epididymis and especially of sperm isolated from that tissue, in healthy, well-fed, fertile
rats maintained on essential fatty acid-sufficient diets. The n−9 polyenes occurred in large concentrations in the choline
glycerophospholipids (CGP), the major phospholipid class of spermatozoa in epididymalcauda, and were highly concentrated in plasmenylcholine, the major subclass of CGP. The uncommon polyene 22∶4n−9 was found in the
highest proportion, followed in order of relative abundance by 22∶3n−9, 20∶3n−9 and 24∶4n−9. These polyenes were probably
derived from oleate (18∶1n−9) in much the same way as long-chain polyenes of the n−6 and n−3 series are derived from linoleate
(18∶2n−6) and linolenate (18∶3n−3), respectively. 相似文献
20.
Ulla I. Brimberg 《Journal of the American Oil Chemists' Society》1993,70(11):1063-1067
The autoxidation of methyl oleate and oleic acid shows some differences as compared to the autoxidation of linoleate,e.g., the formation of water at an early stage. Linearization of experimental data on the autoxidation to high oxidation degrees
of methyl oleate and other monounsaturated substrates shows that the rate equations previously derived for methyl linoleate
in the range of 1–25% oxidation are valid, provided the correct expression for the remaining unreacted substrate is used.
With monounsaturated substrates, part of the oxygen is consumed by a secondary oxidation reaction almost from the beginning,
and only a certain constant fraction α of the total O2 consumption is consumed in hydroperoxide formation. The fraction α is different for methyl oleate, oleyl alcohol, oleic acid
andcis 9-octadecene, but the rate constant for the hydroperoxide formation is the same for all of them when experimental conditions
are the same. The main difference between oleate and linoleate autoxidation is the much faster decomposition of the oleate
hydroperoxides relative to their slow formation. 相似文献