Fatty acid desaturase systems of hen liver and their inhibition by cyclopropene fatty acids

Hen liver preparations which desaturate stearic acid at the 9,10 position to form oleic acid have been found to desaturate other saturated fatty acids of carbon chain length from 12 to 20 and 22. The 9,10-monoenoic fatty acid of the same chain length as the substrate fatty acid is the major product formed. Minor amounts of the 10,11- and 11, 12-monoenoic acids are also formed. Maximum desaturation occurred with the C₁₄ fatty acid substrate and with the fatty acids C₁₇ and C₁₈, suggesting the presence of at least two desaturating systems. The cyclopropene fatty acids, sterculic and malvalic acids, inhibited the desaturation of all thefatty acids at the 9,10 position but desaturation at the 10,11 and 11, 12 positions was affected only slightly. The effect is not due to inhibition of the primary activating enzyme, the long chain acyl CoA synthetase. Sterculic acid is a more effective inhibitor than either malvalic acid or sterculyl alcohol, probably because these cyclopropene compounds do not block the desaturating site of the enzyme as completely as sterculic acid.     

Identification of 18-oxo-9,10-epoxystearic acid,a novel compound in the cutin of young apple fruits

18-Oxo-9,10-epoxystearic acid was identified in the cutin of young apple fruits by hydrogenolysis with LiAlH₄, deuterolysis with LiAlD₄, CrO₃ oxidation of deuterated product followed by reduction with LiAlH₄ and mass spectrometry of the products. Scientific Paper No. 3957, Project 2001, Agricultural Research Center, College of Agriculture, Washington State University, Pullman, Wash.     

Acid-catalyzed conversion of epoxyesters to hydroxyesters

Esters of 9,10-epoxystearic aeid (epoxidized oleic acid), dissolved in 1,4-dioxane, were treated at 15C, first with aqueoiis acid and then with water to convert them to 9,10-dihydroxystearates in high yields. Ester functions remained intact. Glycidyl 9,10-epoxystearate, ethylene glycolbis-9,10-epoxystearate and catecholbis-9,10-epoxystearate were converted to the corresponding tetrahydroxy esters by this method. Treatment of methyl 9,10-epoxystearate with diluted (24%) fluoboric acid gave methyl 9,10-dihydroxystearate in 89% yield. Under similar conditions glycidyl stearate did not react and the internal epoxy group of glycidyl 9,10-epoxystea-rate was hydrated preferentially. Hydration of methyl 9,10-epoxystearate with coned H₂SO₄ led to the formation of considerable amt of byproducts, principally methyl 9(10)-ketostearate. Side reactions were inhibited by diluting the acid-catalyst. Presented at the AOCS Meeting, Minneapolis, 1963. A laboratory of the B. Utiliz. Res.& Der. Dir., ABS, USDA.     

Different behavior between Pt and Pd catalysts in the hydrogenolysis of cyclohexanediones and hydroxycyclohexanones

Hydrogenolysis reactions of cyclohexanediones, hydroxycyclohexanones, and some related alicyclic ketones were studied over Pt, Pd, Ir, and Rh catalysts at atmospheric hydrogen pressure in t-butyl alcohol as a solvent. Pt and Pd had high catalytic activities for the hydrogenolysis of carbon-oxygen bonds. However, Ir and Rh scarcely had any activity unless 1,3-cyclohexanedione and 3-hydroxycyclohexanone were involved. The mechanisms of the hydrogenolysis differed with Pt and Pd. In the hydrogenation of 4-methoxycyclohexanone, Pt afforded cyclohexyl methyl ether as the hydrogenolysis product; while Pd afforded cyclohexanone, which was then hydrogenated to cyclohexanol. Thus Pt cleaved the carbon-oxygen double bond, and Pd cleaved the carbon-oxygen single bond. Deuterolysis of cyclohexanone and 4-methoxycyclohexanone on Pt gave mainly d₂ species of cyclohexane and cyclohexyl methyl ether as the hydrogenolysis products. This indicated that the carbon-oxygen double bonds were directly cleaved to yield methylene groups on Pt. Almost of all 3-hydroxycyclohexanone was hydrogenolyzed to cyclohexanone on Pd; whereas cyclohexanone as well as cyclohexanol was not hydrogenolyzed at all. In the case of Pd, the carbon-oxygen single bond was cleaved when it was activated by formation of π-oxoallyl adsorbed species on the catalyst at the carbon-oxygen double bond.     

Cu-B2O3/SiO2, an effective catalyst for synthesis of fatty alcohol from hydrogenolysis of fatty acid esters

This work demonstrates that Cu- B₂O₃/SiO₂ is an effective catalyst for synthesis of fatty alcohols from hydrogenolysis of fatty acid esters. Boron oxide not only acts as a textural promoter to increase the dispersion of copper, but also as a structural promoter to decrease the activation energy of hydrogenolysis by 10 kJ/mol. The optimum loading of boron oxide doped is around 6.4 wt%. This chromium-free copper catalyst is seven times as active as the commercial copper chromite (Engelhard Cu-1234E) in the hydrogenolysis of methyl esters at 240°C, 110 bar. Cu- B₂O₃(6.4%)/SiO₂ is a promising catalyst for lower pressure (<150 bar) hydrogenolysis processes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Incorporation of oxygen-18 into the oxirane ring ofcis-9,10-epoxyoctadecanoic acid

The synthesis ofcis-9,10-epoxyoctadecanoic acid by tissue slices of wheat plants infected withPuccinia graminis tritici (Wheat stem rust) has been investigated further. Synthetic methylcis-9,10-epoxyoctadecanoate and the same ester isolated from incubation in an atmosphere containing¹⁸O₂, or a medium containing H₂ ¹⁸O, were analyzed by mass spectrometry. These analyses revealed that molecular oxygen was incorporated into the oxirane ring ofcis-9,10-epoxyoctadecanoic acid. Presented in part at the AOCS Meeting, Minneapolis, October 1969.     

Experiments in the formulation of heavy duty liquid detergents from tallow

Several tallow-based detergents were investigated in simplified formulations comprising ca. 10~15% active ingredient, 4% foam stabilizer, 10% isopropyl alcohol, 20% K₄P₂O₇ and 50~55% water, 1% with respect to carboxymethylcellulose. Disodium 2-sulfoethyl α-sulfostearate or sodium oleate could be used as the only active ingredient or in blends with other tallow-based compounds. The presence of a soluble form of the tallow alcohol sulfates, sodium 9,10-dichlorooctadecyl sulfate, gave maximum detergency in hard water. Presented at the AOCS Meeting, Minneapolis, 1963. E. Utiliz. Res. and Dev. Div., ARS, USDA.     

Iron/sulfur-catalyzed coal liquefaction in the presence of alcohol and carbon monoxide

The activities of several iron-based catalyst precursors towards the liquefaction of various kinds of coals, ranging from brown to bituminous, were examined in alcohol–carbon monoxide systems. Pentacarbonyliron (Fe(CO)₅) with or without sulfur, or synthetic pyrite were found to be excellent catalyst precursors. Primary alcohols (ethanol and 1-propanol)–CO acted as an effective hydrogen source, whereas branched alcohols were less effective. In the Fe(CO)₅/sulfur catalyzed liquefaction of Yallourn coal at 375°C for 120 min, a high conversion (99.5%) was achieved in the presence of ethanol and CO (7.0 MPa/cold). The two-staged reaction (375°C, 60 min+425°C, 60 min) further improved the oil yield to 59.1% with a slight decrease in the coal conversion. The uptake of alcohol into asphaltene and preasphaltene fractions was distinctly observed, especially for Illinois No. 6 coal. The infrared analyses of the asphaltene fractions from each coal showed absorption at around 1705 cm⁻¹, characteristic for those obtained in the linear alcohol–CO systems. According to the characterization of the products by NMR and the preliminary study using a model compound, alkylation as well as the hydrogenolysis seem to contribute to the dissolution of coals.     

Deoxygenation of stearic acid with a novel Ni(CO)‐MoS2/Fe3S4 catalyst

Magnetically recyclable Ni(Co)‐promoted MoS₂ catalysts with greigite (G) core were synthesized and their activity and selectivity in hydrodeoxygenation of stearic acid were investigated. The activity of the catalysts tested at 320 °C and H₂ initial pressure of 3.5 MPa could be ranked as NiMo/G > CoMo/G > Mo/G. Two main products were detected, C18 (through HDO pathway) and C17 hydrocarbons (through DCO pathway). HDO was the dominant pathway for all of the catalysts. As for the C18/C17 ratio, the catalysts were found to be in the order: Mo/G > CoMo/G ≈ NiMo/G. The Paraffin/Olefin ratio was over 1 for all of the catalysts with NiMo/G showing the highest ratio. Stearic acid was found to have an inhibiting effect on the adsorption of intermediates over the active sites. Moreover, the concentrations of intermediates decreased at high conversions of stearic acid. The formation of the intermediate aldehyde is through C–O hydrogenolysis of the fatty acid following the protonation, dehydrogenation, and hydride addition steps. The same steps were suggested to be involved in the transformation of the aldehyde to the alcohol. Formation of C_n‐1 hydrocarbons was found to be via decarbonylation route. The enhancement of the DCO pathway over the promoted catalysts was related to the electron transfer from the promoting atom to an adjacent sulphur atom and reduction in sulphur‐metal bond strength.     

Isotope effects in the desaturation of stearic to oleic acid

Comparisons have been made of the rates of desaturation of stearic to oleic acid using a series of differently labeled forms of the substrate and two different methods of assay. The reaction has been measured either by analyzing the amount of labeled oleic acid produced, or by analyzing the amount of tritium released into water from [9,10-³H₂]-labeled substrates. The rate of desaturation of [1-¹⁴C] stearic acid has been compared with that of [threo-9,10-³H₂] and [erythro-9,10-³H₂] stearic acids in which about 99% of the label was at the 9 and 10 positions and in which most of the labeled molecular species contained two tritium atoms. A further series of [erythro-9,10-³H₂] stearates was used in which there was a greater proportion of tritium at positions other than 9 and 10 or a greater proportion of species containing only one tritium atom, or both. In the tritium release assay the enzyme discriminated against the tritium substrates, the discrimination being greater witherythro-ditritio-compounds than with monotritio orthreo-ditritio-compounds. The isotope effect was also observed when [³H] stearoyl-CoA thiol esters were the substrates, and when the source of the enzyme was the green algaChlorella vulgaris. Despite the isotope effect, the release of tritiated water can be used as an assay of desaturase activity. If the absolute value of enzymic activity is required, however, the location and stereochemistry of the tritium atoms should be known or the method standardized against [1-¹⁴C] stearic acid.     

Hydrogenolysis of n-Hexadecane on iron and its inhibition by carbon monoxide

The hydrogenolysis of normal hexadecane was studied over iron at 325° and 355°C. As expected with iron catalysts, the main product was methane, but the selectivities for intermediate alkanes were moderately large, probably due to the length of the carbon chain. Furthermore, gas chromatography—mass spectrometry analysis of the heavier products indicated the presence of alkylbenzenes, alkenes and branched alkanes which accounted for about 20 mole % of the C₉–C₁₃ hydrocarbons. When 5.7 mole % of carbon monoxide was added to the feed, hydrogenolysis reactions were inhibited and products similar to those in the Fischer—Tropsch synthesis were found. Therefore, CO acts like a poison for the hydrogenolysis of hydrocarbons.     

Adsorption characteristics of reduced Mo and Ni–Mo catalysts in the hydrodeoxygenation of benzofuran

The promotional effect of Ni on the hydrodeoxygenation (HDO) of benzofuran (BF) over reduced Ni–Mo/γ-Al₂O₃ catalysts was studied. The adsorption characteristics of Al₂O₃ support, mono-metallic Mo, and bi-metallic Ni–Mo catalysts that were pre-reduced were investigated using the feed molecule (BF) and a probe molecule (NO) as adsorbates. NO was used to probe the coordinatively unsaturated sites (CUS). Three adsorption modes for benzofuran over reduced Al₂O₃ support, Mo, and Ni–Mo catalysts were proposed that involved OH groups, Brønsted acid sites, and CUS, respectively. Benzofuran molecule adsorbed more strongly on B acid sites and CUS than on OH groups and was activated with weakening of the C–O bond. With increasing catalytic hydrogenation activity (increasing CUS) and/or decreasing hydrogenolysis activity (decreasing acidity), the reaction pathway for benzofuran HDO changes from a hydrogenolysis route to a route that involves saturation of the benzene ring before any heteroatom removal takes place.     

HDS of benzothiophene and dihydrobenzothiophene over sulfided Mo/γ-Al2O3

The hydrodesulfurization (HDS) of benzothiophene (BT) and dihydrobenzothiophene (DHBT) was studied over a sulfided Mo/γ-Al₂O₃ catalyst at 5 MPa and 280 and 300 °C. In the absence of H₂S, benzothiophene reacted by hydrogenation to dihydrobenzothiophene and by hydrogenolysis to ethylbenzene (EB), and dihydrobenzothiophene reacted by hydrogenolysis to ethylbenzene. H₂S inhibited both hydrogenation and hydrogenolysis, but the latter much more strongly. The reverse inhibition was observed for 2-methylpiperidine (MPi). In the presence of H₂S and/or 2-methylpiperidine, dihydrobenzothiophene reacted to ethylbenzene as well as by total hydrogenation to octahydrobenzothiophene, and on to ethylcyclohexenes and ethylcyclohexane. Dihydrobenzothiophene did not react back to benzothiophene at and below 300 °C, while the equivalent tetrahydrodibenzothiophene reacted fast to an equilibrium with tetrahydrodibenzothiophene, due to stabilization of the vinylic bond by the alkyl groups. The observed products and kinetic results were explained by a model in which the CS bonds were mainly broken by hydrogenolysis.     

Synthesis of soluble poly(9,10-dihydrophenanthrene-2,7-diyl)s. A new class of luminescent poly(p-phenylene)s with ethylene type bridges

Poly(9,10-dihydrophenanthrene-2,7-diyl)s with -OSi(R)₂(R′) groups at the 9,10-positions were synthesized by dehalogenative polycondensation of the corresponding monomers by using a zerovalent nickel complex. They showed number average molecular weights (M_n's) of 9800-69,000 and high quantum yields (62%-quantitative) in photoluminescence. Palladium catalyzed copolymerization of 2,7-dibromo-9,10-dihydrophenanthrene having -OCH₃ or -OSi(R)₂(R′) groups at the 9,10-positions with diethynyl- or diboronic-aromatic compounds also gave photoluminescent polymers with high quantum yields.     

Electrocarboxylation of 2-methylhalogen-9,10-anthraquinones

Herein we propose a new synthetic route for the production of 9,10-anthraquinone-2-ethanoic acid (AQEA) by electrocarboxylation of 9,10-anthraquinone-2-bromo-methyl (BrMAQ) or 9,10-anthraquinone-2-chloro-methyl (ClMAQ). Electrocarboxylation of anthraquinones appears as an alternative for synthesizing their respective carboxylic acids. Electrosyntheses were carried out using N,N-dimethylformamide (DMF) as solvent, NaClO₄ as electrolyte and metallic magnesium as sacrificial anode. One of electrolysis products was AQEA, which was isolated, purified and then analysed by IR, RMN and high performance liquid chromatography (HPLC). Electrocarboxylation selectivity to AQEA ranged on average from 32 to 40% using ClMAQ and BrMAQ, respectively.     

Physicochemical Study of Glycerol Hydrogenolysis Over a Ni–Cu/Al2O3 Catalyst Using Formic Acid as the Hydrogen Source

Glycerol hydrogenolysis to propanediols requires the use of hydrogen as reactant. One interesting option is to directly generate this hydrogen in active sites of the support using hydrogen donors, such as formic acid. The effect that the reacting pressure has on glycerol conversion and product selectivity over a Ni–Cu/Al₂O₃ catalyst was studied. The negative effect of decreasing the pressure was much more significant when the source of hydrogen was dissolved molecular hydrogen than when it was formic acid. X-ray photoelectron spectroscopy and temperature programmed reduction measurements were performed to understand the effect of Ni–Cu/Al₂O₃ reduction procedure on the catalytic activity. Semi-batch reactor studies with the Ni–Cu/Al₂O₃ catalyst were carried out with continuous addition of the hydrogen donor to obtain kinetic data. Langmuir–Hinshelwood type models were developed to describe the direct conversion of glycerol into propanediol, and propanediol further hydrogenolysis to 1-propanol. The model included the competitive adsorption between both glycols. These models were used to obtain valuable data for the optimization of the process.     

Chlorinated alcohols: II. The chlorination of oleyl alcohol

Chlorination of oleyl alcohol gives mainly 9,10-dichlorostearyl alcohol but a variety of other products are also formed. By-products include 9(10)-(9,10-dichlorostearoxy)-10(9)-chlorostearyl alcohol (14%) and 9,10-dichlorostearyl 9,10-dichlorostearate (3–4%) in addition to three or four less clearly defined products (12%). One group of products is apparently derived from participation of the hydroxyl group in the chlorine addition step while the other products formed by the reaction of the hydroxyl group with chlorine or chlorine and hydrogen chloride.     

Photoinitiated cationic oligomerization of terminal and internal epoxides

The iodonium salt‐catalyzed, photoinduced cationic oligomerization of terminal and internal monoepoxides from oleochemical as well as the petrochemical origin was studied. The ring‐opening of terminal epoxides (1,2‐octene oxide, phenyl glycidyl ether, 9,10‐epoxy decanoic acid methyl ester and 10,11‐epoxy undecanoic acid methyl ester) predominantly led to macrocyclic oligoethers (M_n = 650—1,100 g/mol) via backbiting in quantitative yields. Mixtures of cyclic and bishydroxy‐terminated oligoethers (M_n = 1,050—1,500 g/mol) were achieved by the conversion of internal epoxides (7,8‐tetradecene oxide and cis‐9,10‐epoxy octadecanoic acid methyl ester) in yields of 80—95%. Macrocyclization was completely suppressed by addition of 20 mol‐% water or ethylene glycol receiving diol‐oligoethers for potential application as soft segments for polyurethanes with molecular weights of approximately 1,300 g/mol.     

Inorganic-melt-catalysed hydrogenation of phenanthrene

The hydrogenation of the coal model compound phenanthrene was investigated using a molten hydroxide-carbonate catalyst. The rate of catalysed hydrogenation was found to be approximately an order of magnitude greater than the uncatalysed reaction. Batch experiments were conducted at 20.7 MPa hydrogen pressure in a 1-l top-stirred autoclave at 480 °C for reaction times up to 1 h. Spinning-band distillation and gas-liquid chromatography coupled with mass spectrometry were used to separate and identify reaction products. Principal hydrogenation products were 9,10 dihydrophenanthrene and 1,2,3,4-tetrahydrophenanthrene. In addition, substituted naphthalenes and biphenyls were formed by hydrocracking of these two compounds. A similar product distribution was reported by others for an investigation of the thermal high-pressure hydrogenolysis of phenanthrene. The rate of the thermal reaction, however, was considerably lower.     

Kinetics of two-step methanol synthesis in the slurry phase

The carbonylation of methanol using potassium methoxide catalyst and hydrogenolysis of methyl formate using a copper-chromite catalyst (39% Cu; 37% Cr and 3% Mn) were studied in the temperature ranges of 60–110°C and 100–140°C and pressure ranges of 25–65 and 30–60 bar respectively in a mechanically agitated reactor. Kinetic rate expressions are presented for both reactions. The carbonylation reaction was found to be rapid and limited by equilibrium at the conditions studied. The apparent activation energy for the carbonylation was found to be 67.7 ± 1.5 kJ/mol. CO₂ reacts with the potassium methoxide catalyst and stops the reaction. The hydrogenolysis reaction was found to be slow at the studied conditions with an apparent activation energy of 69.8 ± 2.0 kJ/mol. CO inhibited the hydrogenolysis reaction over the copper-chromite catalyst used. CO₂ poisoned the copper-chromite catalyst. A Langmuir-Hinshelwood type rate model was used to fit the experimental data. A brief discussion of the feasibility of the two-step methanol synthesis in a single stage reactor is given. The data would be useful for evaluating the possibility of synthesizing methanol from H₂ and CO using these reactions either in two separate reactors or concurrently in one reactor.