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1.
Methyl cis-9, cis-12-octadecadienoate (methyl linoleate; c9, c12) and the corresponding cis,trans and trans.trans geometric isomers ( c9, t12 and t9, t12) were hydrogenated at 40 C and atmospheric hydrogen pressure in acetone as solvent, with nonmetallic palladium-on-resin
catalyst. These catalysts were prepared by impregnation of cationic exchange resins with an aqueous solution of palladium
dichloride. The methyleneinterrupted dienes were hydrogenated to the monoene stage with almost infinite selectivity, especially
with c9, c12, whereas t9, t12 was hydrogenated somewhat less selectively. The latter isomer was reduced considerably more slowly than the first, whereas c9, t12 occupied an intermediate position. The hydrogenation proceeded for an important part via a straightforward reduction of
one of the double bonds, though conjugation prior to hydrogenation also occurred. The methylene-interrupted dienes isomerized
to a high degree geometrically during hydrogenation, but they scarcely isomerized positionally, resulting in small amounts
of inactive ethylene-interrupted dienes. 相似文献
2.
Potassium elaidate in slightly alkaline solution was hydrogenated for up to 7 hr with 1.5% of Rufert nickel catalyst at 150
C and 20 kg/sq cm pressure. Potassium linoleate was similarly hydrogenated with 1.0% catalyst for 7 hr, and the hydrogenation
continued for another 7 hr after addition of 0.5% fresh catalyst. Periodic samples from each were analyzed for component acids.
The positional isomers in the cis and trans monoenes, isolated by preparative argentation thin layer (TLC) or column chromatography, were estimated after oxidation to
dicarboxylic acids. Some diene fractions were isolated for further examination. In potassium elaidate hydrogenation, cis monoenes were initially produced in considerable amounts, but to a lesser extent thereafter. Positional isomers were similarly
distributed in both cis and trans monoenes after prolonged hydrogenation. In the hydrogenation of potassium linoleate, a drop in iodine value (IV) of 60 units
occurred in the first hour, and 38% of trans monoenes (in which the 10- and 11-monoenes constitute 32% each) were formed. The IV then fell only slowly, and up to 38%
of cis monoene (mostly 9- and 12-isomers) was formed. Addition of fresh catalyst caused a major shift of cis monoenes to trans forms. The diene fraction was mostly nonconjugated material with the first double bond at the 9, 8 and 10-positions. Minor
amounts of conjugated dienes were present as well as a dimeric product. 相似文献
3.
Methy cis-9-octadecenoate (methyl oleate; c9), methyl cis-9, cis-13-octadecadienoate ( c9, c13) and a 50∶50 mixture of this diene with methyl cis-9, cis-12-octadecadienoate (methyl linoleate; c9, c12) have been hydrogenated on a nonmetallic palladium-onresin catalyst in acetone as a solvent at 40 C and atmospheric hydrogen
pressure. The monoene is hydrogenated very slowly, but c9, c12 is reduced easily and quickly. The ethylene-interrupted diene reacts more slowly than c9, c12, but considerably faster than c9, because active methylene-interrupted dienes are intermediates by double-bond migration. This isomerization process also
results in the formation of inactive polymethylene-interrupted dienes, which accumulate during hydrogenation. Also c9 isomerizes considerably during reduction. In the 50∶50 mixture, c9, c12 is hydrogenated about eight times faster than c9, c13.
The activity of the catalyst for the c9, c12 hydrogenation described previously (1) is considerably higher than that derived from the present data. The experiments
described in this study were carried out about eight months later, so that we have to deal with an older catalyst. However,
reproduction of the catalyst resulted in the same activity. Furthermore, we used a new batch of c9, c12 for these experiments, which was purified in the same way as the previous one. The catalyst is probably sensitive to apolar
compounds which may be present in c9, c12 and which are not removed by alumina. Small amounts of these compounds may have a drastic influence on the activity of
the catalysts under investigation because the catalyst dosing is very low. We emphasize that, though the activity may vary
to some extent (depending on substrate quality), the selectivity and the isomerization pattern do not change. 相似文献
4.
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
5.
The products formed by hydrogenation of methyl cis-9, trans-12- and trans-9, trans-12-octadecadienoates with nickel and platinum catalysts have been compared with those from methyl esters of the naturally
occurring all- cis linoleate. Hydrogen uptake is slower for the trans isomers. Much of the monoene consisted of esters with double bonds at the 9 and 12 positions with their original geometric
configurations. Monoenoic esters with double bonds at the 10 and 11 positions were predominately trans and apparently formed by conjugation before hydrogenation. Nickel produced more isomerization than platinum but less than
previously reported for copper. With both catalysts hydrogenation proceeded both directly and through conjugated intermediates,
in contrast to copper in which all hydrogenation is believed to follow conjugation.
Presented at the AOCS Meeting, Los Angeles, April 1972.
ARS, USDA. 相似文献
6.
The need for a selective catalyst to hydrogenate linolenate in soybean oil has prompted our continuing study of various model
triunsaturated fats. Hydrogenation of methyl β-eleostearate (methyl trans,trans,trans-9,11,13-octadecatrienoate) with Cr(CO) 3 complexes yielded diene products expected from 1,4-addition ( trans-9, cis-12- and cis-10, trans-13-octadecadienoates). With α-eleostearate ( cis,trans,trans-9,11,13-octadecatrienoate), stereoselective 1,4-reduction of the trans,trans-diene portion yielded linoleate ( cis,cis-9,12-octadecadienoate). However, cis,trans-1,4-dienes were also formed from the apparent isomerization of α- to β-eleostearate. Hydrogenation of methyl linolenate (methyl cis,cis,cis-9,12,15-octadecatrienoate) produced a mixture of isomeric dienes and monoenes attributed to conjugation occurring as an intermediate
step. The hydrogenation of α-eleostearin in tung oil was more stereoselective in forming the cis,cis-diene than the corresponding methyl ester. Hydrogenation of linseed oil yielded a mixture of dienes and monoenes containing
7% trans unsaturation. We have suggested how the mechanism of stereoselective hydrogenation with Cr(CO) 3 catalysts can be applied to the problem of selective hydrogenation of linolenate in soybean oil.
No. Market. Nutr. Res. Div., ARS, USDA. 相似文献
7.
A mixture of conjugated dienes, obtained by alkali-isomerization of methyl cis-9, cis-12-octadecadienoate ( c9, c12) has been hydrogenated on a nonmetallic palladium-on-resin catalyst at 40C under atmospheric hydrogen pressure in acetone
as solvent. The results have been used to quantify the contribution of the conjugation mechanims to the hydrogenation process
of c9, c12. In a 50∶50 mixture conjugated dienes are hydrogenated 4.6 times faster than c9, c12 at 40 C. This diene is hydrogenated very selectively both by straightforward reduction of one of the double bonds and by
reduction of conjugated intermediates. The contribution of the former reaction route is more than 50% under the reaction conditions
used. It is assumed that the crucial intermediate in the associative mechanism is formed by hydrogen transfer from the metal
ion to c9, c12 resulting in a chelating ring consisting of an ethylene bridge between the π-coordinated double bond and the σ-coordinated
bond. This σ, π-complex is responsible for the straightforward, selective hydrogenation of c9, c12 as well as for the geometric isomerization of this diene. 相似文献
8.
The catalytic activity and selectivity for hydrogenation of linoleic acid were studied on Ni, Cu, and Pd catalysts. A detailed
analysis of the reaction product was performed by a gas-liquid chromatograph, equipped with a capillary column, and Fourier
transform-infrared spectroscopy. Geometrical and positional isomerization of linoleic acid occurred during hydrogenation,
and many kinds of linoleic acid isomers ( trans-9,trans-12; trans-8,cis-12 or cis-9,trans-13; cis-9,trans-12; trans-9,cis-12 and cis-9,cis-12 18∶2) were contained in the reaction products. The monoenoic acids in the partial hydrogenation products contained eight
kinds of isomers and showed different isomer distributions on Ni, Cu, and Pd catalysts, respectively. The positional isomers
of monoenoic acid were produced by double-bond migration during hydrogenation. On Ni and Pd catalysts, the yield of cis-12 and trans-12 monoenoic acids was larger than that of cis-9 and trans-9 monoenoic acids. On the contrary, the yield of cis-9 and trans-9 monoenoic acids was larger than that of cis-12 and trans-12 monoenoic acids on Cu catalyst. From these results, it is concluded that the double bond closer to the methyl group (Δ12)
and that to the carboxyl group (Δ9) show different reactivity for hydrogenation on Ni, Cu, and Pd catalysts. Monoenoic acid
formation was more selective on Cu catalyst than on Ni and Pd catalysts. 相似文献
9.
CLA is of considerable interest because of reported potentially beneficial effects in animal studies. CLA, while not yet unambiguously
defined, is a mixture of octadecadienoic acids with conjugated double bonds. The major isomer in natural products is generally
considered to be cis-9, trans-11-octadecadienoic acid ( c9, t11), which represents >75% of the total CLA in most cases. Other isomers are drawing increased attention. The t7, c9 isomer, which is often the second-most prevalent CLA in natural products, has been reported to represent as much as 40%
of total CLA in milk from cows fed a high-fat diet. The need for a reference material became apparent in a recent study directed
specifically at measuring t7, c9-CLA in milk, plasma, and rumen. A suitable standard mixture was produced by stirring 0.5 g of γ-linolenic acid (all cis-6,9, 12-C 18∶3) with 100 mL of 10% hydrazine hydrate in methanol for 2.5 h at 45°C. The solution was diluted with H 2O and acidified with HCl. The resulting partially hydrogenated FA were extracted with ether/petroleum ether, dried with Na 2SO 4, and conjugated by adding of 6.6% KOH in ethlylene glycol and heating for 1.5 h at 150–160°C. Approximately 20 mg each of
cis-6, trans-8; trans-7, cis-9; cis-9, trans-11; and rans-10, cis-12 were obtained along with other FA. Methyl esters (FAME) of these four cis/trans isomers were resolved by Ag +HPLC (UV 233) and partially resolved by GC/(MS or FID) (CP-Sil 88). Treatment of these FAME with I 2 yielded all possible cis/trans (geometric) isomers for the four positions 6,8; 7,9; 9,11; and 10,12. 相似文献
10.
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
11.
High oleic (monoene) oils were obtained from soybean oil by selective hydrogenation with copper catalysts. A mixture of nickel
and copper chromite catalyst had activity suitable for producing the high monoene oils. A new catalyst (copper-on-Cab-O-Sil)
prepared in the Laboratory was more active than commercial copper catalysts. Hydrogenated oils contained 61–72% monoenoic
and 14–24% dienoic acids, and there was essentially no increase in stearic acid. The trans-isomer content of these oils varied between 17% to 32%. Double bonds in the monoene were distributed along the molecule from
C 6 to C 15, but were located preferentially in the C 9 position for the cis-monoene and in the C 10 and C 11 positions for the trans-monoene. When the iodine value of these high monoene oils was about 90–95, they remained liquid above 28 C. Citric acid treatment
reduced the copper content of hydrogenated oils to a level that was comparable to that of the original soybean oil.
Presented at the AOCS Meeting, Chicago, October 1967.
Food and Agricultural Organization representative from Rumania.
No. Utiliz. Res. Dev. Div., ARS, USDA. 相似文献
12.
Potassium oleate in slightly alkaline solution was hydrogenated for up to 7 hr with Rufert nickel catalyst at 150C and 20 kg/sq cm pressure. With 1% catalyst, the iodine value dropped by 12 units in the first hour, and only slightly thereafter. With 2% catalyst there was a drop of 24 units in iodine value in the first hour, a steady state for the next 3 hr, and a second sharp drop of 30 units prior to the seventh hour. Samples of fat hydrogenated over 1% catalyst for 3 hr and 7 hr respectively were analyzed by gas-liquid chromatography, the cis and trans monoenes were separated by argentation thin-layer chromatography, and the positional isomers in each were determined by oxidation of the total fraction to dicarboxylic acids, which were then estimated by GLC. Apart from double-bond saturation during the first 3 hr of hydrogenation, extensive double-bond migration yielded 23.5% of trans 8- to 13-monoene, accompanied by small amounts only of positional cis monoenes other than the starting material. After 7 hr of hydrogenation, extensive cis to cis isomerization occurs, accompanied by less cis to trans shift; the cis:trans ratio for each monoene consequently tended toward 1:1. The results are explained on the sorption mechanism of hydrogenation and suggest that soap hydrogenation, involving catalyst poisoning, may represent a magnified version of normal fat hydrogenation. 相似文献
13.
Soybean oil was hydrogenated with a carbon‐supported ruthenium catalyst (Ru/C) at 165 °C, 2 bar H 2 and 500 rpm stirring speed. Reaction rates, trans isomer formation, selectivity ratios and melting behaviors of the samples were monitored. No catalytic activity was found for the application of 10 ppm of the catalyst, and significant catalytic activity appeared at >50 ppm of active catalyst. The catalyst concentration had an effect on the reaction rate of hydrogenation, but the weight‐normalized reaction rate constant ( kc) was almost independent of the catalyst concentration at lower iodine values. Ru/C generated considerable amounts of trans fatty acids (TFA), including high amounts of trans 18:2, and also stearic acid, due to its very non‐selective nature. The selectivity ratios were found to be low and varied between 1.12 and 4.32 during the reactions. On the other hand, because of the low selectivity, higher slip melting points and solid fat contents at high temperatures were obtained than those for nickel and palladium catalysts. Another different characteristic of this catalyst was the formation (max 1.67%) of conjugated linoleic acid (CLA) during hydrogenation. Besides, CLA formation in the early stages of the reactions did not change very much with the lower iodine values. 相似文献
14.
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
15.
Catalytic activity and selectivity for hydrogenation of linoleic acid ( cis-9, cis-12 18:2) were studied on Pt, Pd, Ru, and Ir supported on Al 2O 3. Stearic acid (18:0) and 10 different octadecenoic isomers (18:1) in the products could be separated completely by using a new capillary column coated by isocyanopropyl trisilphenylene siloxane for gas-liquid chromatography. The monoenoic acid isomers and dienoic acid isomers in the products on the various catalysts showed different distributions. The catalysts exhibited nearly equal selectivity for stearic acid formation. The 12-position double bond in linoleic acid has higher reactivity than the 9-position double bond in catalytic hydrogenation on platinum-group metal catalysts. In addition to hydrogenation products of linoleic acid, geometrical and positional dienoic acid isomers ( trans-9, trans-12; trans-8, cis-12; cis-9, trans-13; trans-9, cis-13; cis-9, trans-12 18:2), due to isomerization of linoleic acid during hydrogenation, were contained in the reaction products. Ru/Al 2O 3 exhibited the highest activity for isomerization of linoleic acid with the noble metal catalysts. Conjugated octadecadienoic acid isomers have been observed in products of the reaction on Pt/Al 2O 3, Ru/Al 2O 3, and Ir/Al 2O 3. Catalytic activities of noble metals for positional and geometric isomerization of linoleic acid during hydrogenation decreased in the sequence of Ru ≥ Pt > Ir » Pd. 相似文献
16.
Different Rh complex catalysts were compared for the hydrogenation of methyl sorbate and linoleate in the absence of solvents.
At 100 C and 1 atm H 2 the following complexes, RhCl(Ph 3 P) 3 (Ph= phenyl), [RhClNBD] 2 (NBD=norbornadiene) and RhH(CO)(Ph 3P) 3, produced mainly methyl trans-2-hexenoate (34 to 56%). Their diene selectivity was not particularly high as they produced 14 to 41% methyl hexanoate. With
RhCl(Ph 3 P) 3 constant ratios between rates of methyl sorbate disappearance and formation of methyl trans-2- and trans-3-hexenoate indicate approximately the same activation energy for 1,2-addition of H 2 on the Δ4 double bond of methyl sorbate and for 1,4-addition to this substrate. In the hydrogenation of methyl linoleate
with RhCl(Ph 3 P) 3, the kinetic curves were simulated by a scheme in which 1,2-reduction was more than twice as important as 1,4-addition of
H 2 via conjugated diene intermediates. Although the complexes RhCl(CO)(Ph 3 P) 3 and [Rh(NBD)(diphos)] +PF 6 (diphos=diphosphine) were inactive in the hydrogenation of methyl sorbate, they catalyzed the hydrogenation of methyl linoleate
at 100 C and 1 atm. Catalyst inhibition apparently was caused by stronger complex formation with methyl sorbate than with
the conjugated dienes formed from methyl linoleate. 相似文献
17.
Uncommon cis and trans fatty acids can be desaturated and elongated to produce unusual C 18 and C 20 polyunsaturated fatty acids in animal tissues. In the present study we examined the formation of such metabolites derived
from cis and trans isomers of oleic and linoleic acids of partially hydrogenated vegetable oil origin in rats. For two months, aduut male rats
were fed a partially hydrogenated canola oil diet containing moderately high levels of trans fatty acids (9.6 energy%) and an adequate level of linoleic acid (1.46 energy%). Analysis of the phospholipid (PL) fatty
acids of liver, heart, serum and brain showed no new C 18 polyunsaturated fatty acids, except for those uncommon 18∶2 isomers originating from the diet. However, minor levels (each
<0.3% PL fatty acids) of six unusual C 20 polyunsaturated fatty acids were detected in the tissues examined, except in brain PL. Identification of their structures
indicated that the dietary 9 c,13 t−18∶2 isomer, which is the major trans polyunsaturated fatty acid in partially hydrogenated vegetable oils, was desaturated and elongated to 5 c,8 c,11 c,15 t−20∶4, possibly by the same pathway that is operative for linoleic acid. Furthermore, dietary 12 c−18∶1 was converted to 8 c,14 c−20∶2 and 5 c,8 c,14 c−20∶3; dietary 9 c,12 t−18∶2 metabolized to 11 c,14 t−20∶2 and 5 c,8 c,11 c14 t−20∶4, and dietary 9 t,12 c to 11 t,14 c−20∶2. These results suggested that of all the possible isomers of oleic and linoleic acids in partially hydrogenated vegetable
oils, 12 c−18∶1, 9 c,13 t−18∶2, 9 c,12 t−18∶2 and 9 t,12 c−18∶2 are the preferred substrates for desaturation and elongation in rats. However, their conversions to C 20 metabolites were not as efficient as that of oleic or linoleic acids. 相似文献
18.
A silica-bonded complex was prepared by reacting polyphenylsiloxane with silylated Chromosorb and then with Cr(CO) 6. This complex catalyzed stereoselective hydrogenation of sorbate to cis-3-hexenoate. Soybean methyl esters were hydrogenated at 210 C in cyclohexane to form products high in cis unsaturation. The recovered catalyst could be recycled once with methyl sorbate. IR showed decreased Cr(CO) 3 in the recovered catalysts, and the hydrogenation products contained inactive Cr. 相似文献
19.
Continuous hydrogenation of fats and fatty acids using suspended catalysts was studied in a vertical flow reactor packed with
Raschig rings. A short time of reactive contact of the fat or the fatty acid with the catalyst and hydrogen is the unique
feature of this system. A nickel catalyst used in the hydrogenation of soybean oil gave a reduction of 40-50 iodine value
units per min, small amounts of trans-isorners (10-20%), large proportions of linoleate in unreduced octadecadienoyl moieties (70-80%), and nonselective reduction
of polyunsaturated acyl moieties (linoleate selectivity ratio 1-3). Another nickel catalyst, used in the hydrogenation of
tallow fatty acids, also gave a reduction of 40-50 iodine value units per min and nonselective reduction of polyunsaturated
fatty acids. A copper chromite catalyst used in the hydrogenation of soybean oil gave a reduction of 10-15 iodine value units
per min, low levels of trans- isomers (10-15%), and selective reduction of linolenoyl moieties (linolenate selectivity ratio 4-6). Composition of positional
isomers of cis - and trans-octadecenoyl moieties in partially hydrogenated products obtained both with nickel and copper chromite catalysts reveals
that essentially the same mechanisms of isomerization are involved in continuous hydrogenation at short time of reactive contact
as in batch hydrogenation.
1The terms “linoloyl” and “linolenoyl” are used throughout to designate 9-cis, 12- cis-octadecadienoyl and 9 -cis, 12 -cis, 15 -cis- octadecatrienoyl groups, respectively. 相似文献
20.
The dimethyl disulfide (DMDS) adduct method is one of the convenient and effective methods for determining double bond positions of unsaturated fatty acid methyl esters (FAME) except conjugated FAME. When analyzed using gas chromatography/electron ionization‐mass spectrometry (GC/EI‐MS), unsaturated FAME with DMDS added to the double bonds yields high intensity MS spectra of characteristic ions. The MS spectra of characteristic ions can then be used to easily confirm double bond positions. Here we explore the GC/EI‐MS analysis of the DMDS adducts of methyl linoleate geometrical isomers isolated by high performance liquid chromatography (HPLC) with a silver nitrate column. For C18:2‐ c9, c12 and C18:2‐ t9, t12, DMDS randomly formed adducts with double bonds at either carbon 9–10 or carbon 12–13, but not both at the same time due to steric hindrance. For C18:2‐ c9, t12 and C18:2‐ t9, c12, however, DMDS only formed adducts with the double bond in the cis configuration. Consequently, when analyzing fatty acids with methylene interrupted double bonds, with one double bond in the cis and one in the trans configuration, double bond positions cannot be completely confirmed. 相似文献
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