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1.
T. Nishiguchi T. Tagawa H. Imai K. Fukuzumi 《Journal of the American Oil Chemists' Society》1977,54(4):144-149
The selective hydrogenation of methyl linoleate was studied using indoline and isopropyl alcohol as hydrogen sources. Many
transition metal compounds and metallic palladium were examined as catalysts. High selectivity to monoenes and little formation
oftrans isomers were realized under mild conditions in some reaction systems. For example, the system in which isopropyl alcohol
and RuCl2(PPh3)3 were used as hydrogen donor and catalyst was excellent. Also in the hydrogen transfer from indoline to the linoleate catalyzed
by PdCl2 and (NH4)2PdCl4, high selec-tivity was realized. In the RuCl2(PPh3)3-isopropyl alcohol, (NH4)2PdCl4-indoline and PdCl2-indoline system, methylcis- trans conjugated octadecadienoate was reduced rapidly with complete selectivity, where-as the same hydrogen transfer systems resulted
in little if any reaction with methyl oleate. High selec-tivity in the reduction of linoleate is presumed to be realized through
prior conjugation of the substrate. 相似文献
2.
Significantly increased activity of Cr(CO)6 was achieved for the stereoselective homogeneous hydrogenation of methyl sorbate andtrans,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 methylcis-3-hexenoate, and methyltrans-9,trans-11-octadecadienoate into methylcis-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 CH3CN- and H2-Cr(CO)3 complexes as intermediates for the stereoselective 1,4-addition of hydrogen totrans,trans-conjugated dienes. 相似文献
3.
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 tocis-3-hexenoate. Soybean methyl esters were hydrogenated at 210 C in cyclohexane to form products high incis 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
4.
The need for a selective catalyst to hydrogenate linolenate in soybean oil has prompted our continuing study of various model
triunsaturated fats. Hydrogenation of methylβ-eleostearate (methyltrans,trans,trans-9,11,13-octadecatrienoate) with Cr(CO)3 complexes yielded diene products expected from 1,4-addition (trans-9,cis-12- andcis-10,trans-13-octadecadienoates). Withα-eleostearate (cis,trans,trans-9,11,13-octadecatrienoate), stereoselective 1,4-reduction of thetrans,trans-diene portion yielded linoleate (cis,cis-9,12-octadecadienoate). However,cis,trans-1,4-dienes were also formed from the apparent isomerization ofα- toβ-eleostearate. Hydrogenation of methyl linolenate (methylcis,cis,cis-9,12,15-octadecatrienoate) produced a mixture of isomeric dienes and monoenes attributed to conjugation occurring as an intermediate
step. The hydrogenation ofα-eleostearin in tung oil was more stereoselective in forming thecis,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
5.
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 H2 the following complexes, RhCl(Ph3 P)3 (Ph= phenyl), [RhClNBD]2 (NBD=norbornadiene) and RhH(CO)(Ph3P)3, produced mainly methyltrans-2-hexenoate (34 to 56%). Their diene selectivity was not particularly high as they produced 14 to 41% methyl hexanoate. With
RhCl(Ph3 P)3 constant ratios between rates of methyl sorbate disappearance and formation of methyltrans-2- andtrans-3-hexenoate indicate approximately the same activation energy for 1,2-addition of H2 on the Δ4 double bond of methyl sorbate and for 1,4-addition to this substrate. In the hydrogenation of methyl linoleate
with RhCl(Ph3 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
H2 via conjugated diene intermediates. Although the complexes RhCl(CO)(Ph3 P)3 and [Rh(NBD)(diphos)]+PF6 (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
6.
RuH2(PPh3)4 has been immobilized on swellable polyacrylate matrices to provide heterogenized carboxylate-derivatives. These swellable polymer supported ruthenium (II) complex catalysts have been used in the transfer hydrogenation of aldehydes. Hydrogen donors are formate salt, cyclohexanol, and benzyl alcohol. The catalysts exhibit good activity for hydrogen transfer reduction of aldehydes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
7.
D. S. Raju M. R. Subbaram K. T. Achaya 《Journal of the American Oil Chemists' Society》1970,47(10):374-378
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 thecis andtrans 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 bothcis andtrans 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% oftrans monoenes (in which the 10- and 11-monoenes constitute 32% each) were formed. The IV then fell only slowly, and up to 38%
ofcis monoene (mostly 9- and 12-isomers) was formed. Addition of fresh catalyst caused a major shift ofcis monoenes totrans 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
8.
M. Chatterjee Y. Ikushima T. Yokoyama M. Sato 《Advanced Synthesis \u0026amp; Catalysis》2008,350(4):624-632
Selective hydrogenation of citral to unsaturated alcohol [geraniol (trans) + nerol (cis)] was carried out in supercritical carbon dioxide (scCO2) using an MCM‐41 supported plantinum catalyst (∼1 wt% Pt). A remarkable rate of isomerization of the unsaturated alcohol [nerol (cis) to geraniol (trans)] during the hydrogenation of citral was achieved simply by tuning the density of CO2. Optimum reaction conditions were developed to obtain only geraniol (trans) with a selectivity of 98.8% and citral conversion of 99.8%. A significant change in the cis:trans ratio of the product (1:82.3) from the substrate (1:1.3) was observed depending on the various reaction parameters like carbon dioxide and hydrogen pressure, reactant concentration, reaction time and, particularly, the total selectivity for unsaturated alcohol [geraniol (trans) +nerol (cis)]. It has been observed that the presence of hydrogen is necessary for isomerization. Our results were explained in terms of a density‐dependent, two‐step model. The kinetic behaviour shows that the rate of isomerization was higher in scCO2 compared to other organic solvents and the pure form of geraniol (trans) was obtained exclusively. A probable reaction pathway was proposed in order to explain the isomerization during hydrogenation of citral in scCO2 medium. 相似文献
9.
Senthilkumar Muthaiah Soon Hyeok Hong 《Advanced Synthesis \u0026amp; Catalysis》2012,354(16):3045-3053
An efficient, operatively simple, acceptorless, and base‐free dehydrogenation of secondary alcohols and nitrogen‐containing heterocyclic compounds was achieved by using readily available ruthenium hydride complexes as precatalysts. The complex RuH2(CO)(PPh3)3 ( 1 ) and Shvo’s complex ( 2 ) showed excellent activities for the dehydrogenation of secondary alcohols and nitrogen containing heterocycles. In addition to complexes 1 and 2 , the complex RuH2(PPh3)4 ( 3 ) also showed moderate to excellent activity for the acceptorless dehydrogenation of nitrogen‐containing heterocyclic compounds. Kinetic studies on the oxidation reaction of 1‐phenylethanol using complex 1 were carried out in the presence and the absence of external triphenylphosphine (PPh3). External addition of PPh3 had a negative influence on the rate of the reaction, which suggested that dissociation of PPh3 occurred during the course of the reaction. Hydrogen was evolved from the oxidation reaction of 1‐phenylethanol by using 1 mol% of 1 (88%) and 2 (92%), which demonstrated the possible usage of the catalytic systems in hydrogen generation. 相似文献
10.
cis-bond-producing hydrogenation of polyunsaturates catalyzed by polymer-complexed Cr(CO)3 catalysts
R. A. Awl E. N. Frankel J. P. Friedrich E. H. Pryde 《Journal of the American Oil Chemists' Society》1978,55(7):577-582
cis-Bond-producing chromium carbonyl catalysts were prepared by complexing conventional or macroreticular, styrene-divinylbenzene
copolymers or cross-linked poly (vinyl benzoate) with Cr(CO)6. With one exception, these polymer-Cr(CO)3 catalysts were as selective as the corresponding homogeneous arene-Cr(CO)3 complexes for the formation ofcis-monoenes from methyl sorbate and from conjugated, polyunsaturated fatty esters in cyclohexane. Although several of the polymer
catalysts were very active when fresh, they all lost activity on recycling. They could not be recycled more than two times
before a marked decrease in activity occurred due to loss of Cr, as shown by elemental analysis and infrared absorption in
the recovered catalyst. Thermal analysis indicated instability of the polymer complexes at hydrogenation temperatures. 相似文献
11.
E. N. Frankel R. A. Awl J. P. Friedrich 《Journal of the American Oil Chemists' Society》1979,56(12):965-969
The use of Cr(CO)6 was investigated to convert polyunsaturated fats intocis unsaturated products. With methyl sorbate, the same order of selectivity for the formation ofcis-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 thetrans, trans diene system was particularly high in acetone. However, this solvent was not suitable at elevated temperatures required to
hydrogenatecis, trans- andcis, 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 H2, 1% catalyst in hexane solution), the product contains less than 3% each of linolenate andtrans 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
12.
Samer Saleh Elie Fayad Michle Azouri Jean‐Cyrille Hierso Jacques Andrieu Michel Picquet 《Advanced Synthesis \u0026amp; Catalysis》2009,351(10):1621-1628
The straightforward synthesis of a new donor‐stabilized phosphenium ligand 3d by addition of bromodifurylphosphine to 1,3‐dimethylimidazolium‐2‐carboxylate 1 is described. The obtained ligand exhibits a very strong π‐acceptor character, comparable to that of triphenyl phosphite [P(OPh)3] or of tris‐halogenophosphines, with a νCO(A1) at 2087 cm−1 for its nickel tricarbonyl complex. This ligand, as well as the related 3a which was obtained from chlorodiphenylphosphine, were tested in palladium‐catalyzed aryl alkynylation and in the platinum‐catalyzed selective hydrogenation of chloronitrobenzenes, both in an ionic liquid phase. In C C bond cross‐coupling we observed that the increase of the π‐acceptor character in ligand 3d , due to the introduction of an additional electron‐withdrawing group, provides a very efficient catalyst in the alkynylation reaction of aryl bromides with phenylacetylene, including the deactivated 4‐bromoanisole or the sterically hindered 2‐bromonaphthalene. The catalytic activity decreases with recycling due to the sensitiveness of ligands to protonation in the ionic phase. Conversely, a multiple recycling of the metal/ligand system in non‐acidic media was achieved from platinum‐catalyzed hydrogenation of m‐chloronitrobenzene. The catalytic results obtained by employing the complex of platinum(II) chloride with 3a [trans‐PtCl2( 3a )2] in comparison with the non‐ionic related trans‐tris(triphenylphosphine)platinum dichloride [trans‐PtCl2(PPh3)2] complex clearly indicate that the simultaneous existence of a strong π‐acceptor character and a positive charge within the ligand 3a significantly increases the life‐time of the platinum catalyst. The selectivity of the reaction is also improved by decreasing the undesirable formation of dehalogenation products. This cationic platinum complex trans‐PtCl2( 3a )2 is the first example of a highly selective catalyst for hydrogenation of chloronitroarenes immobilized in an ionic liquid phase. The system was recycled six times without noticeable metal leaching in the organic phase, and no loss of activity. 相似文献
13.
Carbonyl complexes of Cr, Mo and W have been studied as soluble catalysts for the hydrogenation of methyl sorbate and of methyl
esters from soybean oil. With methyl sorbate, relative catalytic activity decreased in the approximate order: mesitylene-Mo(CO)3, cycloheptatriene-Mo(CO)3, cycloheptatriene-Cr(CO)3, bicyclo (2,2,1) hepta-2,5-diene-Mo(CO)4, chlorobenzene-Cr(CO)3, methyl benzoate-Cr(CO)3, mesitylene-W(CO)3, benzene-Cr(CO)3, toluene-Cr(CO)3, mesitylene-Cr(CO)3, and hexamethylbenzene-Cr(CO)3. Order of catalytic activity was related to thermal stability of the complexes during hydrogenation. With mesitylene-M(CO)3 complexes, selectivity varied in the order Cr>Mo>W. Under certain conditions the mesitylene complexes of W, Cr and Mo reduced
methyl sorbate respectively to methyl 2-, 3-, and 4-hexenoates as main products.
The more active and thermally stable Cr(CO)3 complexes catalyzed effectively the hydrogenation of linoleate and linolenate in soybean oil esters with little or no stearate
formation. The hydrogenated products formed with the benzoate complex at 165–175 C contained 50–67% monoene, 18–30% diene,
2–7% conjugated diene, and only 3–7%trans unsaturation. Linolenate-linoleate selectivity values varied from 3 to 5 and linoleate-oleate selectivity from 7 to 80. Monoene
fractions had 40–50% of the double bond in the C-9 position; the rest of the unsaturation was distributed mainly between the
C-10 and C-12 positions. Conjugation is apparently an intermediate step in the hydrogenation of linoleate and linolenate.
The Cr(CO)3 complexes are unique in catalyzing the hydrogenation of polyunsaturated fatty esters to monounsaturated fatty esters of lowtrans content.
Presented at AOCS-AACC Joint Meeting, Washington, D.C. April, 1968.
No. Utiliz. Res. Dev. Div., ARS, USDA. 相似文献
14.
Yoshie Kitayama Masahiro Muraoka Megumi Takahashi Tatsuya Kodama Eriko Takahashi Mutsuo Okamura 《Journal of the American Oil Chemists' Society》1997,74(5):525-529
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 Al2O3. 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/Al2O3 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/Al2O3, Ru/Al2O3, and Ir/Al2O3. 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
15.
S. Koritala 《Journal of the American Oil Chemists' Society》1980,57(9):293-298
The mechanism of hydrogenation at 900~950 psi with copper-chromite catalyst was investigated with pure methyl esters as well
as their mixtures. A comparison of double bond distribution intrans-monoenes formed during hydrogenation of linoleate and alkali-conjugated linoleate revealed that 85~95% of the double bonds
in linoleate conjugated prior to hydrogenation. The mode of hydrogen addition to conjugated triene and diene at high pressure
is similar to that at low pressure but positional and geometric isomerizations of unreduced conjugated esters were less at
high pressure. Geometric isomerization of methyl linoleate and linolenate was considerable at high pressure whereas it was
negligible at low pressure. The absence of conjugated products during hydrogenation of polyunsaturated fatty acid esters resulted
from their high reactivity. Conjugated dienes are 12 times more reactive than the triene, methyl linolenate, and 31 times
more reactive than the diene, methyl linoleate. The products of methyl linolenate hydrogenation were the same as those predicted
by the conjugation mechanism.
Presented at the 70th Annual Meeting of the American Oil Chemists' Society, San Francisco, April 29~May 3, 1979. 相似文献
16.
Kamaluddin Abdur‐Rashid Rongwei Guo AlanJ. Lough RobertH. Morris Datong Song 《Advanced Synthesis \u0026amp; Catalysis》2005,347(4):571-579
The new complexes RuHCl(PPh2CH2CHRNH2)2 and RuHCl(PPh2CH2CHRNH2)(R‐ binap), R=H (Pgly), R=Me [(R)‐Pala] were prepared by the substitution of the PPh3 ligands in RuHCl(PPh3)3 or RuHCl(PPh3)[(R)‐binap] with beta‐aminophosphines derived from amino acids. The complex trans‐RuHCl(Pgly)[(R)‐binap] has been characterized by X‐ray crystallography. The complex trans‐RuHCl[(S)‐Ppro]2 where (S)‐Ppro is derived from proline was also prepared and characterized by X‐ray crystallography. These were used as catalyst precursors in the presence of a base (KOPr‐i or KOBu‐t) for the hydrogenation of various ketones and imines to the respective alcohols and amines with H2 gas (1–11 atm) at room temperature. Acetophenone was hydrogenated to (S)‐1‐phenylethanol in low ee (up to 40%) when catalyzed by the enantiomerically pure complexes. These complexes are especially active in the hydrogenation of sterically congested and electronically deactivated ketones and imines and are selective for the hydrogenation of CO bonds over CC bonds. 相似文献
17.
《Inorganic chemistry communications》2000,3(7):397-399
The reaction of cis-[PtCl2(PPh3)2] and NaSePh in benzene produces a mixture of cis- and trans-isomers of the monomeric platinum complex [Pt(SePh)2(PPh3)2]. The low-temperature X-ray structures of both isomers are reported. The structure of cis-[Pt(SePh)2(PPh3)2] is the first crystallographic characterized cis-isomer of mononuclear platinum(II) complex containing only non-chelating organoselenolato and phosphine ligands. 相似文献
18.
Gas chromatography (GC) is used for the analysis of trans-fatty acids in partially hydrogenated vegetable oils. Although trans-isomers of C18 carbon length predominate in partially hydrogenated vegetable oils, trans-isomers of C20 and C22 carbon length occur in partially hydrogenated fish oil. We report a simple silver ion chromatographic combined with capillary
GC technique for quantitative analysis of trans-monoenes derived from partially hydrogenated fish oil. Silver nitrate thinlayer chromatographic (TLC) plates are developed
in toluene/hexane (50∶50, vol/vol). Fatty acid methyl esters are separated into saturates (R
f 0.79), trans-monoenes (R
f 0.49), cis-monoenes (R
f, 0.27), dienes (R
f, 0.10), and polyunsaturated fatty acids with three or more double bonds remaining at the origin. The isolated trans-monoenes are quantitatively analyzed by capillary GC. The technique of argentation TLC with GC analysis of isolated methyl
esters is highly reproducible with 4.8% variation (i.e., coefficient of variation, CV%) in R
f values and 4.3 and 6.9% CV% in quantification within batch and between batch, respectively. Furthermore, the combined technique
revealed that direct GC analysis underestimated the trans-content of margarines by at least 30%. In this study, C20 and C22
trans-monoenes were found in relatively large quantities; 13.9% (range 10.3–19.6%) and 7.5% (range 5.3–11.5%), respectively, in
margarine purchased in 1995, but these C20 and C22
trans-monoenes were much reduced (0.1%) in a fresh selection of margarine purchased in 1998. Compositional data from labels underestimated
the trans-content of margarines, especially those dervied from hydrogenated marine oil. Low levels of C20
trans-monoenes (range 0.1–0.3%) and C22
trans-monoenes (range 0.0–0.1%) were identified in adipose tissue obtained from healthy volunteers in 1995, presumably indicating
consumption of partially hydrogenated fish oil. 相似文献
19.
Yoshie Kitayama Masahiro Muraoka Megumi Takahashi Tatsuya Kodama Hirofumi Itoh Eriko Takahashi Mutsuo Okamura 《Journal of the American Oil Chemists' Society》1996,73(10):1311-1316
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 orcis-9,trans-13; cis-9,trans-12; trans-9,cis-12 andcis-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 ofcis-12 andtrans-12 monoenoic acids was larger than that ofcis-9 andtrans-9 monoenoic acids. On the contrary, the yield ofcis-9 andtrans-9 monoenoic acids was larger than that ofcis-12 andtrans-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
20.
Yoshie Kitayama Megumi Takahashi Hisashi Sugiyama Tatsuya Kodama Mutsuo Okamura 《Journal of the American Oil Chemists' Society》1998,75(1):27-32
Catalytic hydrogenation of linoleic acid was studied on Ir/Al2O3. A detailed analysis of geometrical and positional isomers of octadecenoic acid (18:1) in the products was performed by capillary
gas-liquid chromatography with a new capillary column coated with isocyanopropyl trisilphenylene siloxane (TC-70). Well-resolved
peaks of 10 species of 18:1 were observed in the product. In addition to monoenoic acid isomers, four species of trans-dienoic isomers and conjugated dienoic isomers were found. From the distribution of 18:1 isomers, it was found that the double
bond closer to the methyl end (Δ12) showed higher reactivity than that closer to the carboxyl end (Δ9) for hydrogenation.
Because cis-8 18:1 and trans-8 18:1 were not observed but cis-10 18:1 and trans-10 18:1 were observed in the products, the double-bond Δ9 did not migrate to the carboxyl end but migrated to the methyl
end. On the other hand, the Δ12 bond migrated to both methyl and carboxyl ends. From the distribution of 18:1 isomers in the
reaction pathway, the hydrogenation of linoleic acid proceeds via half-hydrogenation states. Cis-18:1 isomers were produced predominantly in the initial stage of the reaction, while trans-18:1 isomers were produced during progress of the reaction. The cis/trans and positional isomerization took place by readsorption of 18:1 produced by the partial hydrogenation of linoleic acid. 相似文献