Useful direct conversion of tetrahydropyranyl ethers of fatty alcohols into fatty acids

Tetrahydro-2-pyranyl ethers from fatty primary alcohols can be converted in a one-step procedure into the corresponding carboxylic acids in high yields. This process avoids the synthesis of symmetrical esters, particularly for long-chain compounds. This reaction proved to be useful, for instance, to produce polyunsaturated fatty acids immediately before their biological testing.     

Studies on the preparation and analysis of glyceryl ether derivatives and the isolation and reductive ozonolysis of unsaturated glyceryl ethers

Glyceryl ethers were identified and quantified by the GLC analysis of their alkyl iodide (special conditions described), acetonide and allyl alkyl ether derivatives. The acetoxy-mercuri-methoxy derivatives of unsaturated glyceryl ether swere separated from saturated glyceryl ethers by TLC and the fractions were analyzed as alkyl iodides. Monoiodides from saturated glyceryl ethers and diiodides from unsaturated glyceryl ethers were also separated by TLC and then analyzed. Allyl alkyl ethers had small retention volumes and these derivatives were separated into pure fractions by preparative GLC. Ozonides were reduced either to alcohols with lithium aluminum hydrodie or to aldehydes with dimethyl sulfide. The alcohols were converted to mono- and diiodides which were separated by TLC and analyzed by GLC. The recovery of n-C₆ and n-C₇ monoiodides was not quantitative. Diiodides and aldehydes were both identified and quantified by GLC. Ozonolysis data suggest that the 16∶1 glyceryl ethers from dogfish liver oil contain 7,8 and 9,10 isomers and the 18∶1 glyceryl ethers contain 9,10 and 11,12 isomers. Presented in part at the AOCS Meeting, Philadelphia, October 1966.     

A convenient synthesis of long-chain 1-O-Alkyl glyceryl ethers

A convenient and economical procedure for synthesis of long-chain 1-O-alkyl glyceryl ethers (V) is described. Alkyl glycidyl ethers (II) which were derived from the reaction of alcohols (I) with epichlorohydrin using a phase transfer catalyst were first converted into the corresponding dioxolanes (III) or 1-O-alkyl-2,3-di-O-acetylglycerols (IV). Subsequent hydrolysis of the resultant products provided 1-O-alkyl glyceryl ethers (V) in high yields.     

添加剂对MgAlON材料抗氧化性能的影响

MgAlON材料较易被氧化 ,研究了几种抗氧化剂的作用。结果表明 :B4 C和SiC的效果最好 ,它们氧化后分别生成B2 O3、SiO2 及其化合物 ,填充于材料气孔 ,起着保护作用 ,使得MgAlON材料的氧化性质由连续性变成保护性     

Gas chromatographic separation of linoleic acid hydroperoxides as trimethylsilyl ethers of methyl hydroxystearates

The primary products, 9- and 13-hydroperoxy-octadecadienoic acids, from lipoxygenase catalyzed oxidation of linoleic acid, were converted into the trimethylsilyl ethers of methyl 9- and 13-hydroxystearates which were completely separated by gas chromatography on an OV-17 methyl silicone (50% phenyl groups), capillary column.     

Effects of zinc chloride on the cleavage of ether structures present in coal

A number of compounds which model the ether structures found in coal were subjected to reaction in the presence of ZnCl₂. Both cyclic and non-cyclic ethers reacted, provided that at least one methylene group was present adjacent to the ether oxygen atom. Complete elimination of oxygen to form water was achieved with dibenzyl and cycloaliphatic ethers, but oxygen bonded directly to a phenyl or naphthyl group was converted to an unreactive phenolic hydroxyl group.     

Long chain n- Alkyl monoaza crown ethers

Homogeneous polyoxyethylated long chain alkylamines with 5 to 7 oxyethylene units were prepared by the reaction between oligoethylene glycol monochlorides and alkylamines. They were converted to the corresponding long chain N-alkyl monoaza crown ethers by treatment withp-toluene-sulfonyl chlorides in the presence of alkali metal hydroxides in dioxane. The physical and spectral properties of these new derivatives of alkylamines were investigated in detail.     

Metabolism of alkyl glyceryl ethers in the rat

The metabolism of¹⁴C- and³H-labeled alkyl glyceryl ethers after intraperitoneal injections was examined in the liver and intestine of the rat. Additionally, in vitro experiments were conducted with intestinal homogenates and intetinal contents. From these investigations it was concluded that the liver and the intestine metabolize the alkyl glyceryl ethers very differently. Intestinal contents can alter α-batyl alcohol, as indicated by preliminary experiments, and intestinal cells contain enzyme systems which convert the alkyl glyceryl ethers to the mono- and di-acyl derivatives. Very little esterified glyceryl ethers were found in the liver lipids. The intestine contains an enzyme system which, although it has a greater specificity for chain length and for isomeric position of the ether than that of the liver system, does cleave the glyceryl ethers. From in vivo studies, of intestinal tissue it was concluded that all of the injected glyceryl ethers were converted intact the ethanolamine, serine, and choline alkyl glyceryl ether phospholipids; with the use of α-batyl alcohol, the phosphatidyl ethanolamine fraction, contained most of the labeled glyceryl ether phospholipid with β-batyl alcohol, α-chimyl, and β-chimyl alcohols, the phosphatidyl, choline fraction contained most of the labeled alkyl glyceryl ether phospholipid. No significant amount (<1%) of labeled alkyl glyceryl ether phospholipids was found in any of the rat-liver lipids. Predoctoral trainee supported by Public Health Service Training Grant 5TI-GM-404-04 from the National Institute of General Medical Sciences, National Institutes of Health. Work done in partial fulfillment of the Ph.D. in the Department of Biochemistry at the University of North Carolina.     

The preparation and characterization of the methoxy derivatives of polyunsaturated fatty acids: Stabilized product analogs of lipoxygenase catalysis

The products from the action of soybean lipoxygenase on a series of polyunsaturated fatty acids have been converted in 2 steps into the corresponding methoxy derivatives. The product hydroperoxides were reduced in situ to alcohols with sodium borohydride. The ethers were generated by treatment of the alcohols with sodium hydride and methyl iodide in tetrahydrofuran. 13-Methoxy-9(Z),11(E)-octadecadienoic, 15-methoxy-11(Z),13(E)-eicosadienoic and 15-methoxy-5(Z),8(Z),11(Z), 13(E)-eicosatetraenoic acids were thus prepared. The methyl ethers were analyzed and the structures established by high performance liquid chromatography, nuclear magnetic resonance and infrared spectrometry, polarimetry and mass spectroscopy (as methyl esters). The methylation reaction proceeds without molecular rearrangements or racemiziation.     

Selective aerobic oxidations by supported ruthenium hydroxide catalysts

Aerobic oxidations of various alcohols, diols, and amines are efficiently promoted by the easily prepared inexpensive supported ruthenium hydroxide catalysts. A wide variety of substrates including aromatic, aliphatic, and heterocyclic ones can be converted into the desired products in moderate to excellent yields without the need for additives such as bases and electron/hydrogen transfer reagents. The catalysis for these reactions was intrinsically heterogeneous, and supported ruthenium hydroxide catalysts recovered after these reactions could be reused without appreciable loss of the catalytic performances. A reaction mechanism involving ruthenium alkoxide (amide) formation/β-elimination has been proposed for the present catalytic oxidations.     

Diversity‐Oriented Synthesis of Functionalized 1‐Aminopyrroles by Regioselective Zinc Chloride‐Catalyzed,One‐Pot ‘Conjugate Addition/Cyclization’ Reactions of 1,3‐Bis(silyl enol ethers) with 1,2‐Diaza‐1,3‐butadienes

In a convenient one‐pot process, the easily accessible 1,2‐diaza‐1,3‐butadienes and 1,3‐bis(silyl enol ethers) are converted into the previously unknown functionalized 1‐aminopyrroles and 1‐amino‐4,5,6,7‐tetrahydroindoles. The domino reaction proceeds through a zinc chloride‐catalyzed ‘conjugate addition/cyclization’ sequence.     

Formation of N- and O-methyl derivatives of lipids containing amino,amide or hydroxy groups by the pyrolytic reaction with trimethylsulfonium hydroxide

Base-catalyzed transesterification of acyl lipids with methanol in the presence of trimethylsulfonium hydroxide (TMSH) is an easy and convenient method for the preparation of fatty acid methyl esters for GC analyses. However, lipids containing functional groups such as amino, amide and hydroxy groups are converted in varying degrees to the corresponding N- and O-methyl derivatives by the pyrolytic reaction of TMSH occurring in the injector of the gas chromatograph. For example, lipids containing amino or amide groups are converted into the corresponding N-methyl and N,N-dimethyl derivatives, fatty acid ethanolamides to the corresponding N-methyl, O-methyl and N,O-dimethyl derivatives, whereas alkyl methyl ethers are formed from long-chain alcohols. Furthermore, 2-O- and 3-O-monomethyl ethers as well as 2,3-di-O-methyl ethers are formed from 1-O-alkylglycerols, methoxy fatty acid methyl esters from hydroxy fatty acids as well as steryl 3β-O-methyl ethers from cholesterol and other sterols. Since some of the mentioned artefacts may interfere with fatty acid methyl esters in GC separations the TMSH derivatization method is recommended only with caution for lipids containing amino, amide and hydroxy groups. The methylation reactions, which finally lead to the corresponding N-methyl, O-methyl, N,N-dimethyl or N,O-dimethyl derivatives of fatty acids and lipids may, however, be of some diagnostic value for the structural analysis of such lipids by GC/MS.     

混配组分对基于KH2PO4/Al2O3催化剂的酚油醚化的影响

以KH2PO4/Al2O3为催化剂,针对以甲醇为烷基化试剂的酚油醚化体系,研究了5种混配组分(乙酸、甲酸、丙酮、呋喃、乙酸乙酯)对酚油醚化反应规律的影响。结果表明,丙酮对促进烷基酚转化为芳醚的作用效果最强。基于丙酮混配组分,500℃下探究了丙酮质量配比的影响,基于最佳丙酮添加量(50wt%),进一步考察了温度对反应体系的影响,并进行机理分析。结果表明,丙酮含量不高于70wt%时,液体收率随丙酮含量升高而降低,进一步提高丙酮含量时液体收率基本稳定。各丙酮含量下,液体产物中均未检出邻甲氧基苯酚或其它任何烷氧基酚。较高丙酮含量时烷基酚含量显著降低。丙酮含量为50wt %时,芳醚含量出现极大值(29.06area%),进一步提高丙酮含量,芳烃及其它组分显著增加,导致产物中芳醚含量降低。随反应温度升高,产物中的芳醚和芳烃含量分别在500和450℃时出现极大值。综合考虑液体收率和产物极性两方面因素,确定该反应体系的最佳反应温度为450℃,丙酮添加量为50wt%,最佳条件下产物中芳醚与芳烃总量达52.90area%。丙酮分子中的羰基与酚系物中的羟基发生作用,分解产生CO2,同时烷基酚与烷氧基酚脱羟基后分别得到芳烃和芳醚两类主要液相产物。     

Kinetic study of domestic limestone (Daesung)

Sulfidation and sulfation reactions of Daesung limestone, which is a calcium-based sorbent chosen out of domestic limestone for the removal of H₂S and SO₂, were investigated by using TGA (thermal gravimetric analyzer) Effects of H and H₂S on the sulfidation were also investigated The conversion rate of CaS to CaSO₄ in oxidation was low since the concentration of SO₂ used for this study was low and CaO was not completely converted into CaS It was observed that the effects of H₂ concentration on the sulfidation were relatively small and the maximum conversion rate and reaction rate increased with increase of H₂S concentration In the sulfation reaction, conversion rate could be raised with the injection of air at a sulfation reaction temperature above 800 °C However, the conversion rate decreased without the injection of air due to the blockage of sorbent pores.     

Synthesis of Ether-Diols with Low Polarity from Long-Chained Fatty Alcohols for Use in Block Copolymers

Diol-terminated polyethers are important intermediates for the manufacturing of block copolymers, but only a few polyethers other than polyethylene glycols are available on a technical scale. Most of them are highly polar. Natural fatty alcohols—converted to similar polyethers—should have a grossly reduced polarity because of a large separation of the oxygen atoms in the C18 chain. A synthesis sequence of polyethers with a longer carbon chain compared to the ethylene glycol-derived ethers based on commercially available fatty alcohols was designed for a future examination of the hydrophobic properties. Palladium-catalyzed cleavage of olefinic dialkyl carbonates results in carbon dioxide elimination and subsequent formation of ethers from an allyl-palladium cation. It could be shown that this process with fatty alcohols like undec-10-en-1-ol or oleyl alcohol can be run with appreciable yield. Although carbonates were obtained here using expensive chloroformates as starting materials, transesterification of dimethylcarbonates can be used similarly. Ruthenium-catalyzed acyclic diene metathesis (ADMET) at both chain terminations then was applied to polymerize the ethers. Depending on the alkenyl chain, short oligomers with a degree of polymerization (DP) of about 5–8 seem to be formed according to gel permeation chromatography (GPC).     

Chemical modification of chitosan: Synthesis and characterization of chitosan‐crown ethers

Four novel Schiff‐type chitosan (CTS)‐crown ethers were synthesized through a reaction between ? NH₂ in CTS or crosslinked chitosan (CCTS) and ? CHO in 4′‐formylbenzo‐crown ethers, and four secondary‐amino‐type CTS‐crown ethers were prepared through the reduced reaction of NaBH₄, respectively. Their structures were characterized by elemental analysis, Fourier transform infrared (FTIR) spectra analysis, solid‐state ¹³C‐NMR analysis, and X‐ray diffraction (XRD) analysis. The elemental analysis results showed that the percentage of nitrogen in all CTS‐crown ethers were lower than that of CTS or CCTS. From the FTIR data of CTS, CCTS, and CTS‐crown ethers I–VIII, we saw that the characteristic peaks of C?N, N? H, and Ar appeared and that the characteristic peaks of pyranoside in the chain of CTS or CCTS were not destroyed. The XRD spectra demonstrated that CTS‐crown ethers I–VIII gave lower crystallinities than CTS or CCTS, which indicated that these compounds were considerably more amorphous than CTS or CCTS. In the solid‐state ¹³C‐NMR spectra, all of these CTS‐crown ethers had a particular peak of aromatic at 128 or 129 ppm, and the greatest difference between Schiff‐type CTS‐crown ethers and secondary‐amino‐type CTS‐crown ethers was that the Schiff‐type CTS‐crown ethers had the particular peak of C?N, which disappeared in secondary‐type CTS‐crown ethers. All these facts confirmed that the structures of CTS‐crown ethers I–VIII were as expected. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2221–2225, 2003     

Disterylether – Artefakte der Fettbleichung

Disteryl Ethers – Artifacts of Bleaching of Fats and Oils (1) Disteryl ethers are formed by acid catalyzed dehydration of Δ⁵-unsaturated sterols during the bleaching of fats and oils with acid-activated bleaching earths. These artifactual lipids can be used as markers of the bleaching process. Distanyl ethers can be produced by catalytic hydrogenation of Δ^5,5'-unsaturated disteryl ethers. (2) Spectroscopic characterization of disteryl ethers and distanyl ethers showed that these steroidal lipids are highly symmetrical compounds with the oxygen atom of the ether linkage in the center of symmetry. Conformation of C-O bonds at the ether bridge is 3β/3'β showing that both types of compounds are periplanar and voluminous molecules. (3) Mixtures of disteroid ethers are separated by silver ion HPLC into the unsaturated disteryl ethers and the saturated distanyl ethers. Individual components of these two classes of disteroid ethers are separated by capillary GLC. Determination of individual compounds may be a conclusive proof of bleaching and hydrogenation of fats and oils. (4) Di[4,4'-¹⁴ C]cholesteryl ether and di [4,4'-¹⁴C]sitosteryl ether, intragastrically administered to mice, were found to be neither absorbed nor metabolized in the gastrointestinal tract. Both dicholesteryl ether and disitosteryl ether, fed to mice at a level of 400 mg/kg body weight x day for 4 weeks, did not lead to ill effects in the animals.     

Electrochemical cells as reactors for selective oxygenation of hydrocarbons at low temperature

New oxidation methods for the partial oxidation of alkenes at low temperatures (<373 K) using gaseous alkene–O₂ fuel cell systems and for hydroxylation of alkanes and aromatics applying H₂–O₂ fuel cell reactions are shown. Catalytic oxidation systems can be converted into electrochemical cells which control the reaction rate and selectivity by a variable resister or potentiostat in the outer circuit, as shown for the Wacker type and π-allyl type oxidations. The hydroxylation of benzene to phenol and of light alkanes could be realized at room temperature by applying H₂–O₂ fuel systems. The reverse H₂–O₂ cell reaction enables the epoxidation of propylene into porpylene oxides. It is also possible to combine the two reactions for the cogeneration of phenol and epoxide. Some problems to develop these processes on a commercial scale are also discussed.     

Reaction of lipids containing hydroxy groups with trimethylsulfonium hydroxide: Formation ofO-methyl derivatives

Base-catalyzed transesterification of acyl lipids with trimethylsulfonium hydroxide (TMSH) is an easy and convenient method for the preparation of fatty acid methyl esters (FAME) for gas chromatography (GC) analyses. We have found, however, that lipids containing hydroxy groups are partially converted to the correspondingO-methyl ether derivatives which may interfere with FAME in GC separations. For example, long-chain alcohols are found to be converted to alkyl methyl ethers,rac-1-O-alkylglycerols to the corresponding 2-O-and 3-O-monomethyl ethers, as well as 2,3-di-O-methyl ethers, hydroxy fatty acids to methoxy FAME, and cholesterol to cholesteryl 3β-methyl ether. From our results, it is obvious that TMSH derivatization method is not recommended without limitation for lipids containing hydroxy groups; it may be, however, of some diagnostic value for the analysis of such lipids by GC/mass spectrometry.     

Air-sintered silicon (Si)-bonded silicon carbide (SiC) hollow fiber membranes for oil/water separation

In this work we evaluated the effect of adding Si as sintering additive into SiC for producing air-sintered hollow fiber membranes. According to crystallographic analyses, SiC and Si were converted to SiO₂ after sintering at 1350 °C. The addition of 30 wt% of Si into SiC ceramic material promoted the binding of SiC particles and improved the membrane mechanical resistance to 42.25 ± 3.39 MPa after air sintering at 1350 °C. The produced asymmetric ceramic membrane presented a packed pore-network and micro-voids with pore sizes of 1.73 and 5.29 μm, respectively. The filtration of an oil/water emulsion enabled oil retention 98.75 ± 0.95 %. Cake formation was the main fouling occurrence and membrane regeneration with equivalent oil retention and similar steady sate flux was achieved after water cleaning under ultrasound irradiation. Thus, the use of Si as air-sintering aid was favorable for producing Si-bonded SiC hollow fiber membranes with suitable application for oil/water separation.