共查询到20条相似文献,搜索用时 15 毫秒
1.
Isomeric dienes and monoenes produced by partial hydrogenation of linolenic acid have been separated by the combined use of
low-temp crystallization and countercurrent distribution. Cis, trans dienes have been separated from cis, cis dienes. Cis, cis conjugatable dienes have been partially separated from cis,cis nonconjugatable dienes. Dienes with one trans double bond were separated by gas chromatography into two groups: cis, trans and trans, cis. Individual positional isomers could not be separated.
Cis-9 monoene was separated from cis-12, cis-15, and trans monoenes by low-temp crystallization. Countercurrent distribution at 3,000 transfers only partially separated this mixture
of cis-12, cis-15, and trans monoenes. The double bond in both cis and trans monoenes was found in all carbon positions, 7 through 16, showing for the first time that the 15, 16 bond of linolenic acid
had moved away from the carboxyl. The major cis bonds remained at carbons 9, 12, and 15.
Combination of countercurrent distribution fractions has produced samples containing 95% cis, cis dienes; 90% cis, trans or trans, cis dienes; 95% cis monoenes; and 90% trans monoenes.
Presented at the AOCS meeting at Chicago, Ill., 1961.
A laboratory of the No. Utiliz. Res. & Dev. Div., ARS, U.S.D.A. 相似文献
2.
13C Nuclear magnetic resonance spectroscopy has been used in a nondestructive investigation of conjugated unsaturated acids
in seed oil triacylglycerols. Spectra of seven seed oils, from Punica granatum, Cucurbita palmata, Jacaranda mimosifolia, Centranthus ruber, Catalpa bignonioides, Chilopsis linearis and Calendula officinalis, containing among them six isomeric trienoic acids, cis,trans,cis- and trans,trans,cis-8,10,12-, cis,trans,cis-, cis,trans,trans-, trans,trans,cis- and trans,trans,trans-9,11,13-octadecatrienoic acids, and of the oil of Impatiens balsamina containing cis,trans,trans,cis-9,11,13,15-octadecatetraenoic acid, have been examined. Structures of component acids were derived from shifts of double
bond carbons and of carbons close to the double bond systems. Compositions of the oils were obtained from signal intensities.
Results were similar to those obtained by older methods. Only oil of Centranthus ruber contained more than one major conjugated acid; both cis,trans,trans- and trans,trans,trans-9,11,13-octadecatrienoic acids were found. The latter acid is now thought to occur naturally.
Presented in part at the International Society for Fat Research/American Oil Chemists' Society World Congress, New York, 1980.
NRCC no. 20405. 相似文献
3.
Significantly increased activity of Cr(CO) 6 was achieved for the stereoselective homogeneous hydrogenation of methyl sorbate and trans,trans-conjugated fatty esters at ambient temperature and pressure by exposing the catalyst to UV irradiation (3500 Å) in a solvent mixture of cyclohexane-acetonitrile (20:1). In this solvent mixture, methyl sorbate was converted quantitatively at ambient conditions into methyl cis-3-hexenoate, and methyl trans-9, trans-11-octadecadienoate into methyl cis-10-octadecenoate (99.9%). These products are expected by 1,4-addition of hydrogen. Under these conditions no hydrogenation of methyl linoleate occurred. Under the same conditions, cycloheptatriene-Cr(CO) 3 showed lower activity than Cr(CO) 6, and Mo(CO) 6 and mesitylene-Mo(CO) 3 showed no significant activity toward conjugated substrates. When Cr(CO) 6 and Mo(CO) 6 were irradiated at 2537 Å they caused the geometric isomerization of methyl sorbate without hydrogenation, but had no effect on methyl linoleate. A hydrogenation mechanism is proposed for Cr(CO) 6 that involves CH 3CN- and H 2-Cr(CO) 3 complexes as intermediates for the stereoselective 1,4-addition of hydrogen to trans,trans-conjugated dienes. 相似文献
4.
β-Eleostearate and trans,trans-conjugated diene were reduced with deuterium in the presence of copper chromite. Considerable exchange of hydrogen atoms
of the starting material for deuterium atoms was observed. Conjugated double bond systems isomerized (positional and geometric)
extensively during hydrogenation. Isomerization and exchange reactions occurred at a faster rate than hydrogen addition reaction.
During early stages of the reaction, a large amount of the product formed contained no deuterium. Of the three possible mechanisms
of hydrogen addition to β-eleostearate (1,2; 1,4 and 1,6), no one mechanism could account for all the products formed. Reduction of trans-9, trans-11-octadecadienoate at a higher temperature and pressure (200 C, 500 psi) caused a minimum of exchange and isomerization
apparently due to sintering of the catalyst. Monoenes were formed from trans,trans-conjugated diene by both 1,2 and 1,4 addition. Methyl oleate was not reduced, but extensive isomerization occurred. Deuterium
was incorporated into isomeric monoenes. Mechanistic schemes are proposed to account for exchange, isomerization and hydrogen
addition.
Presented in part at the AOCS Meeting, New Orleans, April 1970. 相似文献
5.
Hydrogenation of linseed and soybean methyl esters was achieved at 100–180C, 100–1000 psi H 2 and 0.05–0.25 moles catalyst per mole of ester. The relative activity of metal acetylacetonates in decreasing order was:
nickel (III), cobalt (III), copper (II) and iron (III). Reduction occurred readily in methanol solution but only slowly in
dimethylformamide and acetic acid. No reduction occurred in the absence of solvents. Soybean oil was also hydrogenated rapidly
with nickel (III) acetylacetonate in methanol, but in this system the triglycerides were converted to methyl esters. Nickel
(III) acetylacetonate was the most selective catalyst toward linolenate hydrogenation. Methyl linoleate and linolenate hydrogenated
with nickel(III) acetylacetonate were fractionated into monoenes, dienes and trienes. The cis monoenes separated in 62 to 68% yield had double bonds in the original position. The remaining trans monoenes had extensively scattered unsaturation. The dienes and trienes showed no conjugation, but some of the double bonds
in the dienes were not conjugatable with alkali. Little stearate was formed.
Presented at AOCS meeting in Chicago, 1964
No. Util. Res. and Dev. Div. ARS, USDA 相似文献
6.
Many studies have been published on the effect of antioxidants on unsaturated fatty acid esters but the differences of the
effects of antioxidants on geometric isomers have never been investigated. In this study, methyl cis-9, cis-12-octadecadienoate and its trans isomer methyl trans-9, trans-12-octadecadienoate were used as methyl nonconjugated dienoates, and BHA, BHT, PG, NDGA, 4,4′-dihydroxy-3,5,3′,5′-tetratert-butyl
diphenyl methane, L-thyroxine sodium salt, a-tocopherol and sesamol were used, as antioxidants. The differences of the effects of antioxidants on both geometric isomers
were investigated by determining the induction period using the weighing method. Also determined were the infrared and ultraviolet
spectra, peroxide values, conjugated diene contents, isolated trans double bond contents and molecular weights for the controls and the samples containing antioxidants. The cis,cis isomer was more easily autoxidized and had a shorter induction period than the trans,trans form. By the end of the induction period, no isolated trans double bond forms in the cis,cis isomer, but a considerable amount of isolated trans double bond decreased in the trans,trans isomer. In general, the effects of antioxidants, except NDGA, on the cis,cis isomer were larger than the trans,trans form. 相似文献
7.
Oil of Fevillea trilobata has the composition palmitic acid 31%, stearic acid 12%, oleic acid 11%, linoleic acid 7%, cis,trans,cis 9,11,13-octadecatrienoic acid 30% and cis,trans,trans-9,11,13-octadecatrienoic acid 9%. The oil was analyzed and components identified by 13C NMR spectroscopy; the composition was also confirmed by conventional methods. Assignment of 13C NMR signals of conjugated trienoic acids is discussed and it is shown that mixtures of isomeric conjugated acids can be
analyzed by this method.
NRCC No. 17797. 相似文献
8.
The use of Cr(CO) 6 was investigated to convert polyunsaturated fats into cis unsaturated products. With methyl sorbate, the same order of selectivity for the formation of cis-3-hexenoate was demonstrated for Cr(CO) 6 as for the arene-Cr(CO) 3 complexes. With conjugated fatty esters, the stereoselectivity of Cr(CO) 6 toward the trans, trans diene system was particularly high in acetone. However, this solvent was not suitable at elevated temperatures required to
hydrogenate cis, trans- and cis, cis-conjugated dienes (175 C) and nonconjugated soybean oil (200 C). Reaction parameters were analyzed statistically to optimize
hydrogenation of methyl sorbate and soybean oil. To achieve acceptable oxidative stability, it is necessary to reduce the
linolenate constituent of soybean oil below 1–3%. When this is done commercially with conventional heterogenous catalysts,
the hydrogenated products contain more than 15% trans unsaturation. By hydrogenating soybean oil with Cr(CO) 6 (200 C, 500 psi H 2, 1% catalyst in hexane solution), the product contains less than 3% each of linolenate and trans unsaturation. Recycling of Cr(CO) 6 catalyst by sublimation was carried through three hydrogenations of soybean oil, but, about 10% of the chromium was lost
in each cycle by decomposition. The hydrogenation mechanism of Cr(CO) 6 is compared with that of arene-Cr(CO) 3 complexes.
Presented in part at Seventh Conference on Catalysis in Organic Syntheses, Chicago, Illinois, June 5–7, 1978. 相似文献
9.
The following products are formed during partial reduction of α-eleostearic acid with hydrazine: cis,trans-9,11-octadecadienoic and trans,trans-11,13-octadecadienoic acids; cis-9-, trans-11- and trans-13-octadecenoic acids; and stearic acid. The double bonds are reduced individually in the conjugated triene and also in the
conjugated dienes that are formed. However, the reduction is selective since the trans-11 double bonds in the conjugated triene is reduced only slightly to yield the isolated 9,13-diene.
The trans double bond of the cis,trans conjugated diene reduces at a faster rate than the cis bond. No differences were observed in the rate of reduction of the cis-9 and trans-13 bonds in the triene or of the bonds in the trans,trans conjugated diene.
No. Utiliz. Res. & Dev. Div., ARS, USDA. 相似文献
10.
Heat treatment of sunflower oil resulted in the formation of linoleic geometrical and positional isomers. These isomers were
isolated using a combination of column chromatography, urea fractionation, high performance liquid chromatography (HPLC) on
a C18 reverse phase column and silver nitrate thin layer chromatography (TLC). Each component was submitted to hydrazine reduction
and the resulting monoenes to AgNO 3-TLC. The resulting cis and trans fractions were submitted to ozonolysis in BF 3-MeOH in order to determine the position of the ethylenic bonds. The major isomers were the cis, trans and trans, cis 18∶2 Δ9, 12, the trans, trans 18∶2 Δ9, 12 and some cis, trans, trans, cis and trans, trans 18∶2 conjugated dienes. The cis, trans and trans, cis conjugated dienes were the Δ9, 11, Δ10, 12, Δ11, 13 and Δ12, 14 while the trans, trans isomers were the Δ9, 11, Δ10, 12 and Δ11, 13. These C18∶2 isomers also were detected in oils collected from restaurants and
market vendors.
Presented in part at the AOCS/JOCS annual meeting in Honolulu, Hawaii, in May 1986. 相似文献
11.
Alkali-conjugated linoleate ( cis-9, trans-11- and trans-10, cis-12-octadecadienoate) was hydrogenated with nickel, palladium and platinum catalysts. The trans and cis monoenes formed during reduction were isolated, and their double bond distribution was determined by reductive ozonolysis
and gas liquid chromatography. About 44–69% of the monoenes were composed of δ 10 and δ 11
trans monoene isomers, whereas the δ 9 and δ 12
cis monoenes amounted to 20–26%. With nickel catalyst, composition of monoene isomers remained the same, even when the hydrogenation
temperature was increased. The monoene isomer profiles between nickel and palladium catalysts were indistinguishable. Isomerization
of monoenes with platinum catalyst was suppressed at 80 psi. The position of the double bonds in unreacted conjugated diene
was always retained, except with nickel at both temperatures and with platinum at 150 C when a slight migration occurred.
Geometrical isomerization to trans,trans-conjugated diene was observed in the unreacted diene with nickel (ca. 15% of diene) at both 100 C and 195 C, and with platinum
(ca. 7% of diene) at 150 C.
ARS, USDA. 相似文献
12.
Fractionation of products obtained from partial catalytic hydrogenation of methyl cis-9, cis-12-octadecadienoate (9c,12c-18:2) with tris(triphenylphosphine) chlororhodium [RhCl(Ph 3P) 3] provided a facile method for preparation of a nearly equal molar mixture of methyl cis-9- and cis-12-octadecenoate (9c-18∶1 and 12c-18∶1). Isolation of products was achieved by silver resin and C18 reverse phase liquid
chromatography. Catalytic deuteration of 9c,12c-18∶2 yields a mixture of 9c-18∶1-12,13-d 2 and 12c-18∶1-9,10-d 2 with an isotopic purity of 85%. Final isolated yield of the mixture of 9c- and 12c-18∶1 products was 30%. Isolation of products
from partial hydrogenation of conjugated octadecadienoates (9c,11t-18∶2 or 10t,12c-18∶2) provided a convenient method for
synthesis of an almost equal molar mixture of methyl trans-10 and trans-11-octadecenoate (10t-18∶1 and 11t-18∶1). Characterization of the reaction products from hydrogenation of 9c,12c-28∶2 indicates
that the 9c- and 12c-18∶1 products are formed by the expected 1,2-hydride addition. The presence of small amounts of 10t-
and 11t-18∶1 and conjugated octadecadienoates was evidence for a secondary isomerization-1,4-hydride addition pathway. Isolation
and characterization of products from RhCl(Ph 3P) 3-catalyzed hydrogenation of 9c,11t-18∶2 and 10t,12c-18∶2 indicate that both 1,2- and 1,4-hydride addition to the conjugated
diene isomers occurs at about equal rates, but only the cis bond is reduced by the 1,2-hydride addition pathway and the 1,4-hydride addition pathway yields only a trans-18∶1. Because of this unusual selectivity for a cis bond conjugated with a trans bond, hydrogenation of both 9c,11t-18∶2 and 10t,12c-18∶2 yields the same mixture of t-18∶1 isomers. 相似文献
13.
Hydrogenation of commercial groundnut oil refining soapstock over nickel catalyst is described. The extent of hydrogenation depended on the catalyst concentration present. Residual dienes were greatly altered, and dimers were also formed. With sufficient catalyst, trans monoenes arose from both dienes and cis oleate, but with insufficient catalyst, only from the latter. During the later stages of hydrogenation, cis and trans monoenes each appeared to equilibrate independently to the same isomer distribution. 相似文献
14.
Methyl cis-9, cis-15-octadecadienoate was used as a model for the hydrogenation of methyl linolenate. Homogeneous catalysis by platinum, palladium
and nickel complexes produced a mixture of isomeric monoenes similar to that from the hydrogenation of methyl linolenate.
These catalysts are, therefore, capable of promoting isomerization of isolated double bonds and of producing conjugated dienes
which are necessary for the formation of monoenes.
N. Market, and Nutr. Res. Div., ARS, USDA. 相似文献
15.
Methyl oleate and methyl elaidate, as well as other monoene cis and trans isomers of fatty esters, can be separated quickly and conveniently by a preparative chromatographic procedure in which a
silver-saturated ion-exchange resin is used. Separations are based on differences in stabilites of the silver-olefin complexes.
Recoveries of better than 95% were made, and pure trans and cis monoene fractions were collected. This method can be used to separate saturates from cis and trans monoenes. The cis,trans,cis,cis, and trans,trans-9-12-octadecadienoates were separated. While cis,trans and trans,trans dienes were cluted separately, the cis,cis diene isomer remained on the column.
Presented at AOCS Meeting, in Minneapolis, 1963.
A laboratory of the No. Utiliz. Res. and Dev. Div., ARS, USDA. 相似文献
16.
Analytical methods to obtain the detailed compositions of the fatty acids in oils containing more than one conjugated octadecatrienoic
acid by open-tubular gas liquid chromatography (GLC) and by reversed-phase high performance liquid chromatography (HPLC) were
established. Effective GLC separations of cis,trans,trans-9,11,13-octadecatrienoic acid ( ctt-9,11,13–18∶3), ctc-9,11,13–18∶3, ttc-9,11,13–18∶3, ttt-9,11,13–18∶3, ttc-8,10,12–18∶3, and ttt-8,10,12–18∶3 were obtained with an opentubular column coated with the nonpolar liquid phase OV-1 using an instrument having
all-glass carrier gas pathways. The HPLC method also gave satisfactory separations for the isomeric conjugated octadecatrienoates
on the basis of number of the cis and trans double bonds. Two or three minor conjugated trienoic acids were found along with the principal conjugated trienoic acid in
tung oil, and seed oils of cherry, Prunus sp., Momordica charantia, Trichosanthes anguina, Punica granatum, Catalpa ovata, and Calendula officinalis. The mechanism for the formation of the conjugated trienoic acid mixtures in the seed oils is discussed. The C. ovata seed oil also contained ct and tt-9,12-octadecadienoic acids. The tt isomer is presumed to be a precursor of ttc-9,11,13–18∶3, the main conjugated trienoic acid in this oil. 相似文献
17.
Iron pentacarbonyl is an effective homogeneous catalyst for the reduction of polyunsaturated fats. Hydrogenation of soybean oil and its methyl esters has been achieved at 180C, hydrogen pressures of 100-1,000 psi, and 0.05–0.5 molar concentrations of catalyst. Analyses of partially reduced products show considerable isomerization of double bonds, reduction of linolenate and linoleate with little or no increase in stearate, and accumulation of cis,trans- and trans, trans-conjugated dienes, and isolated trans monoenes. The unreduced trienes include diene conjugated fatty esters. The nonconjugated dienes contain large amounts of trans and nonalkali conjugatable unsaturation. Considerable scattering of double bonds is evident in different fractions between the C 4 and C 16 positions. Complex formation between iron carbonyl and unsaturated fats is also indicated. The course of the homogeneous hydrogenation catalyzed by iron pentacarbonyl appears similar to the heterogeneous catalytic reaction. Metal carbonyls are well known for their isomerizing effects and their ability to form stable complexes with olefins. These homogeneous complexes provide suitable model systems to study the mechanism of catalytic hydrogenation of fats. 相似文献
18.
Methyl linolenate was hydrogenated with 10% copper chromite catalyst at 150 C and atmospheric hydrogen pressure. The product
was separated into monoene, diene and triene fractions by countercurrent distribution. These fractions were further separated
into various geometrical isomers. The double bond location in the various fractions was determined by reductive ozonolysis.
Double bonds in both cis and trans monoene fractions, as well as in cis,trans and trans,trans conjugated dienes, were extensively isomerized. A monoene containing vinylic unsaturation was one of the major products.
The nonconjugated dienes were mostly dienes whose double bonds were widely separated. Results are explained on the basis of
conjugation of the double bonds in linolenate followed by hydrogen addition.
Presented in part at the symposium “Hydrogenation Process,” Division of Industrial Engineering Chemistry, 157th American Chemical
Society Meeting, Minneapolis, April 1968.
No. Utiliz. Res. Dev. Div., ARS, USDA. 相似文献
19.
Determination of the relative reaction rates of isomeric methyl octadecadienoates is possible by competitive reduction of a mixture containing an inactive diene and a radioactively labeled isomer. The hydrogenation rate of methylcis-9,cis-12-octadecadienoate with platinum and nickel catalysts is compared to the hydrogenation rate of each of several isomers of methyl octadecadienoate, and the relative rate of the competitive hydrogenations is calculated by a digital computer. Methylcis-9,cis-12 linoleate is reduced the most rapidly of all the dienes studied. The relative rates of the positional isomers tend to decrease with the increasing number of methylene groups between the double bonds, except when one of the double bonds is in the more reactive 15 position. Comparison of the geometric isomers shows thattrans,trans diene is hydrogenated at a slower rate thancis,cis linoleate. 相似文献
20.
α-Tocopherol and 1,4-cyclohexadiene were tested for their effect on the thermal decomposition of methyl linoleate hydroperoxide
isomers. The volatiles generated by thermolysis in the injector port of a gas chromatograph at 180°C were analyzed by capillary
gas chromatography. In the presence of either α-tocopherol or 1,4-cyclohexadiene, which are effective donors of hydrogen by
radical abstraction, volatile formation decreased in all tests, and significant shifts were observed in the relative distribution
of products in certain hydroperoxide samples. When an isomeric mixture of methyl linoleate hydroperoxides ( cis, trans and trans, trans 9- and 13-hydroperoxides) was decomposed by heat, the presence of α-tocopherol and 1,4-cyclohexadiene caused the relative
amounts of pentane and methyl octanoate to decrease and hexanal and methyl 9-oxononanoate to increase. A similar effect of
α-tocopherol was observed on the distribution of volatiles formed from a mixture of the trans,trans 9- and 13-hydroperoxides. This effect of α-tocopherol was, however, insignificant with pure cis,trans 13-hydroperoxide of methyl linoleate. The decrease in total volatiles with the hydrogen donor compounds, α-tocopherol and
1,4-cyclohexadiene, indicates a suppression of homolytic β-scission of the hydroperoxides, resulting in a change in relative
distribution of volatiles. The increase in hexanal and methyl 9-oxononanoate at the expense of pentane and methyl octanoate
in the presence of hydrogen donor compounds supports the presence of a heat-catalyzed heterolytic cleavage (also known as
Hock cleavage), which seems to mainly affect the trans,trans isomers of linoleate hydroperoxides. 相似文献
|