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1.
P. Van Der Plank A. Van Der Ent A. L. Onderdelinden H. J. Van Oosten 《Journal of the American Oil Chemists' Society》1980,57(10):343-349
Methylcis-9,cis-12-octadecadienoate (methyl linoleate;c9,c12), itst10,t12 andt10,c12 isomers and methylcis-9-octadecenoate (methyl oleate;c9) were hydrogenated with rhodium complexes, the active species of which consisted of [RhL2]+ and [RhL2H2]+ with ligands L=P(C2H5)2C6H5 (catalyst A) P(i-C4H9)3 (catalyst B) and P(CH3)3 (catalyst C). Using these catalysts the influence of steric effects on the reaction mechanism of hydrogenation of dienes
was studied. The reactions were carried out in 2-propanol at atmospheric hydrogen pressure and ambient temperature. During
hydrogenation ofc9 on catalysts A and B, geometrical isomerization mainly occurred, whereas on catalyst C some positional isomerization also
took place.C9,c12 was almost exclusively hydrogenated via conjugated intermediates on catalyst A. On catalyst C, one of the double bonds
was hydrogenated directly, in most cases. In the absence of hydrogen, catalysts A and B conjugatedc9,c12 very fast. The conjugation activity of catalyst C was much lower. Catalyst C showed a high 1,5-shift activity for the conjugatedcis, trans andtrans, cis intermediates during hydrogenation, in contrast to catalysts A and B, which showed a poor activity in this respect.T10,t12 was hydrogenated almost exclusively via 1,4-addition of hydrogen to thecisoid conformation, whereas only a slight preference was found in this mechanism over 1,2-addition for the hydrogenation oft10,c12. On the sterically unhindered catalysts A and C thetrans double bond int10,c12 was preferentially hydrogenated whereas on catalyst B, with its bulky ligands, thecis double bond was reduced faster than thetrans double bond. 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.
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
4.
Summary A high degree of hydrogenation of a polypentenamer was achieved with a homogeneous catalyst based on a metal alkyl-transition metal complex . Essentially complete saturation of the polymer was achieved without significant changes in molecular weight or molecular weight distribution.Presently Senior Humboldt Fellow, Institut für Makromolekulare Chemie, Universität Freiburg, West-Germany 相似文献
5.
《Inorganic chemistry communications》2000,3(3):132-135
Acyclic imines were hydrogenated with rhodium and iridium complexes modified with chiral phosphite and phosphonite ligands. Iridium neutral precursors provided better activities than the analogous cationic complexes, although enantioselectivity was not induced. 相似文献
6.
A. F. Mabrouk H. J. Dutton J. C. Cowan 《Journal of the American Oil Chemists' Society》1964,41(2):153-158
The homogeneous hydrogenation of sodium sorbate, with pentacyanocobaltate II used as the catalyst, was followed manometrically at room temperature and atmospheric hydrogen pressure. One mole of hydrogen was absorbed by one mole of sorbate. UV and IR analyses demonstrated the reduction of sorbate to hexenoate. Gas liquid chromatography (GLC) of hexenoate indicated 82, 17, and 1% yields of 2-,3-, and 4-hexenoates, respectively, with traces of sorbate. Increasing either the period of hydrogenation or the ratio of catalyst to sorbate, or both, did not cause the formation of caproate or change the ratio of the three isomers. Homogeneous catalytic hydrogenation in methanolic solutions showed higher selectivity since 2-hexenoate was present in 96% yield. To standardize GLC columns, hexenoic acid isomers were synthesized by the Knoevenagel condensation.Trans- 2- hexenoic andtrans- 3- hexe- noic acids were prepared in 75 and 85% yields by a condensation ofn-butanal and malonic acid in the presence of pyridine and triethanolamine, respectively.Trans- i- h.exea.oic acid was prepared in 70% yield by condensing diethyl malo-nate with crotyl bromide. Physical properties, including UV and IR spectra, were determined for the purified synthetic acids and methyl esters. Although the absolute specificity of attack at the 4,5-double bond of sorbic acid was not confirmed, the high degree of selectivity obtained does encourage further study of homogeneous catalysis on higher fatty acids. 相似文献
7.
Sapar R. Konuspaev Khairulla N. Zhanbekov Natalya V. Kul'Kova Dmitry Yu. Murzin 《化学工程与技术》1997,20(2):144-148
The kinetics of the liquid phase hydrogenation of 4-tert-butylphenol to form cis- and trans- 4-tert-butylcyclohexanol at 1.0–10.0 MPa and 40°C in isopropanol over a Rh catalyst has been studied. The kinetic behavior of this parallel system is described by a proposed reaction network. Keto-enol tautomeric transformation of adsorbed 4-tert-butyltetrahydrophenol and 4-tert-butylcyclohexanone is thought to be a key step, which governs the stereoselectivity of the overall complex reaction of alkylphenol hydrogenation. 相似文献
8.
《Inorganic chemistry communications》2007,10(9):989-992
Two novel dicarbonyl rhodium complexes with 3,6-di-tert-butyl-o-semiquinones containing back bonded –OCH3 and –F substituents were synthesized and characterized. The number of analogous dicarbonyl-o-semiquinonato rhodium complexes is discussed from the viewpoint of the phenomenon of “bending crystals”. 相似文献
9.
Wilkinson-type rhodium catalysts with various mono and bidentate phosphine ligands have been synthesized starting from [(COD)RhCl]2 and (COD)RhCl(PPh3) as the precursors. Those ligands containing an ethoxysilane group could function as linkers for immobilizing the rhodium complexes on silica and alumina. All polycrystalline and amorphous materials have been investigated by solid-state NMR spectroscopy. The catalytic activity of the complexes, both in homogeneous phase and immobilized, has been determined using the hydrogenation of 1-dodecene, 2-cyclohexen-1-one, and 4-bromostyrene. The homogeneous and immobilized rhodium catalysts with monodentate, as well as dppe- and dppp-type phosphine linkers all showed similar activity. For the immobilized catalysts larger average pore sizes of the support (100Å) led to faster reactions as compared with smaller pores (e.g. 40Å). The reaction times in single batchwise runs could be reduced substantially by diluting the immobilized catalysts on the support surfaces. This measure also prolonged the lifetime of the catalysts when being recycled. Their recyclability is further improved by the chelate linkers, which prevent leaching of the metal moiety. As another reason for catalyst deactivation during recycling the oxidation of the phosphine linkers has been detected by solid-state NMR.Invited contribution to the special volume entitled The Interface between Heterogeneous and Homogeneous Catalysis stemming from the 11th International Symposium on Relations between Heterogeneous and Homogeneous Catalysis. 相似文献
10.
Catalytic isomerization of safflower oil with rhodium complexes 总被引:1,自引:0,他引:1
Cationic rhodium (I) complexes of the type [(NBD)RhL2]+ ClO4
− (NBD, norbornadiene; L, triphenyl phosphine or diphenyl phosphino ethane) have been studied as catalysts for the isomerization
of methyl linoleate and safflower oil. The catalysts gave very good yields of conjugated products with both oil and methyl
linoleate. Isomerization could be carried out under very mild conditions (55–65 C, 1 atm N2). Although the catalyst undergoes transformation in the course of the reaction, it maintains its catalytic activity. In fact,
the catalysts isolated from the reaction with safflower oil were recycled with practically no loss of activity. 相似文献
11.
《Inorganic chemistry communications》2008,11(11):1401-1404
The coordination properties of a donor stabilized-phosphenium adduct have been examined in rhodium chemistry. The preparation as well as the characterization of the first examples of donor stabilized-phosphenium rhodium(I) complexes is reported in this paper. Indeed, mono- and di-cationic rhodium complexes were obtained in quantitative yield by the direct addition of this imidazolium P(III)-ligand to [RhCl(1,5-COD)]2 in CH2Cl2 solution with a 1:1 P/Rh ratio under argon and 2:1 P/Rh ratio under CO atmosphere, respectively. Crystal structure of the bis-cationic donor stabilized-phosphenium rhodium(I) complex has been obtained from an acetone/pentane mixture. Its molecular structure has revealed a particular arrangement in which the chloride atom is sandwiched between both imidazolium rings as a result of the electrostatic attractive interactions between the electron-deficient heterocarbene moieties and the electron rich halide atom. On the other hand, the basicity of N-donor-phosphenium adducts has been evaluated by measure of the CO stretching frequency in one rhodium complex, and was found halfway between the phosphites and the strong π-acceptor phosphines. 相似文献
12.
E. N. Frankel Hiroshi Itatani John C. Bailar Jr. 《Journal of the American Oil Chemists' Society》1972,49(2):132-133
Methylcis-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
13.
Yasuaki Okamoto Hiroyuki Onimatsu Masao Hori Yukiko Inui Toshinobu Imanaka 《Catalysis Letters》1992,12(1-3):239-243
Tricarbonyl chromium (0) species encaged in LiX or NaX was found to be highly efficient and stereoselective for the hydrogenation of butadiene at > 230 K. The selectivity to cis-2-butene depended both on the reaction temperature and butadiene pressure. The reaction mechanism is proposed, in which cis-2-butene is formed via (4-C4H6)Cr(CO)3, while 1-butene via (2-C4H6)Cr(CO)3 and (2-C4H6)2Cr(CO)3. 相似文献
14.
15.
E. N. Frankel Helen M. Peters E. P. Jones H. J. Dutton 《Journal of the American Oil Chemists' Society》1964,41(3):186-191
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 ofcis,trans- andtrans, trans-conjugated dienes, and isolatedtrans monoenes. The unreduced trienes include diene conjugated fatty esters. The nonconjugated dienes contain large amounts oftrans and nonalkali conjugatable unsaturation. Considerable scattering of double bonds is evident in different fractions between the C4 and C16 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
16.
E. A. Emken E. N. Frankel R. O. Butterfield 《Journal of the American Oil Chemists' Society》1966,43(1):14-18
Hydrogenation of linseed and soybean methyl esters was achieved at 100–180C, 100–1000 psi H2 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. Thecis monoenes separated in 62 to 68% yield had double bonds in the original position. The remainingtrans 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
17.
S. Koritala 《Journal of the American Oil Chemists' Society》1985,62(3):517-520
Soybean oil was hydrogenated with palladium acetylacetonate at 60–170 C, 150 psi hydrogen and 1–60 ppm palladium. The best
linolenate selectivity (KLe/KLo=3.5−3.7) was found at 80–120 C. At 120 C palladium acetylacetonate hydrogenated faster than the heterogeneous Pd-on-carbon
catalyst.Trans isomerization with the homogeneous catalyst was much higher compared to Pd-on-carbon catalyst. The low activity of the palladium
complex at low temperatures was improved with the addition of triethylaluminum. Among other metal acetylacetonates tested
only nickel and chromium were mildly active, whereas cobalt and copper were devoid of catalyst activity. 相似文献
18.
不对称催化氢化反应具有完美的原子经济性和清洁高效等特点,是最受青睐的不对称合成方法之一。C=C、C=O、C=N的不对称加氢反应仍主要依赖过渡金属催化剂。过渡金属催化剂,尤其是铑催化剂,催化碳碳双键的不对称加氢反应仍是一个不断发展的领域。本文对近年来利用铑催化剂催化烯烃进行不对称氢化反应的研究进展进行了综述,着重介绍了铑-双膦配体催化体系催化烯烃不对称加氢反应的催化机理,以及铑催化剂在烯胺、不饱和羧酸及衍生物、烯醇酯和非官能团烯烃不对称氢化中的应用,并通过对现有文献的总结指出了今后铑催化剂催化烯烃氢化反应的研究重点,即:①铑-单膦配体催化烯烃不对称氢化反应的作用机理须待提出;②非官能化底物不对称催化氢化反应的手性配体亟待拓宽。 相似文献
19.
E. N. Frankel E. P. Jones V. L. Davison E. Emken H. J. Dutton 《Journal of the American Oil Chemists' Society》1965,42(2):130-134
Homogeneous hydrogenation of unsaturated fats by cobalt carbonyl has been compared with the previously reported catalysis
by iron carbonyl. Soybean methyl esters, methyl linoleate and linolenate have been hydrogenated at 75–180C, 250–3,000 psi
H2 and 0.02 molar concn of catalyst. The cobalt carbonyl catalyst is more active at lower temp than iron carbonyl. The partially
reduced products are similar to those observed with iron carbonyl, but the reaction differs in showing much less accumulation
of conjugated dienes, no selectivity toward linolenate, almost complete absence of monoene hydrogenation to saturates, less
double bond migration and moretrans isomerization. No evidence was found for a stable complex between cobalt carbonyl and unsaturated fats as previously observed
with iron carbonyl. The rates of hydrogenation/double bond were the same for linoleate and linolenate on one hand, and for
alkali-conjugated linoleate and nonconjugated linoleate on the other.
Presented at AOCS Meeting in Minneapolis, 1963.
A laboratory of the No. Utiliz. Res. & Dev. Div., ARS, USDA. 相似文献
20.
C. Bello L. L. Diosady W. F. Graydon L. J. Rubin 《Journal of the American Oil Chemists' Society》1985,62(11):1587-1592
Dichlorodicarbonylbis (triphenylphosphine) ruthenium (II), RuCl2 (CO)2 (PPh3)2, was investigated as a catalyst for edible oil hydrogenation in a preliminary screening of potential catalysts for producing
partially hydrogenated fats with lowtrans-isomer content. Refined, bleached and deodorized canola oil was hydrogenated using 1.77 × 10−5 − 6.64 × 10−4 mol/kg-oil of ruthenium catalyst equivalent to 1.79 × 10−4 − 6.71 × 10−3 wt% Ru. The effects of temperature (50–180 C) and pressure (50–750 psig) on reaction rate,trans-isomer content and fatty acid composition were examined. The activities of RuCl2 (CO)2 (PPh3)2 and nickel (Nysel HK-4 and AOCS standard nickel catalyst) were compared on a molar basis. At 4.40 × 10−4 mol/kg-oil (0.0026 wt/Ni or 0.0044 wt% Ru), 140 C and 50 psig, the nickel catalysts were completely inactive, but the ruthenium
catalyst produced an IV drop of 40 units in 60 min. At 110 C, 750 psig and 1.34 × 10−4 mol/kg-oil (1.35 × 10−3 wt% Ru), a hydrogenation rate of 0.89 ΔIV/min and a maximumtrans-isomer content of 10.4% (IV=45.0) was obtained with the ruthenium catalyst. 相似文献