Der Reaktionsverlauf bei der Hydrierung von Triglyceriden Simultanhydrierung von Tri- und Monolinolenin

Course of Reaction During Hydrogenation of Triglycerides — Simultaneous Hydrogenation of Tri- and Monolinolenin Mixtures of trilinolenin and dipalmitomonolinolenin were subjected to hydrogenation. Argentation chromatography resolved the reaction products into two fractions, each containing one of the starting materials and their hydrogenated products. The relative rate of hydrogenation of linolenic acid in both glycerides could be determined by gas chromatography of the transesterified fractions. It was possible to draw conclusions on the course of reaction using mathematical models for various reaction mechanisms, which have been derived earlier¹. Considerable differences in the behaviour of different catalysts were observed. The results could be explained by assuming equal probability of binding of all the glycerides on the catalyst. Depending on the type of catalyst used, spontaneous hydrogenation of several linolenoyl moieties occurred to varying degree.     

The identification of radiolytic decomposition products from tributyrin

In order to facilitate the detection of radiolytic products of triglycerides which may be of higher molecular weight than their precursor, a low molecular weight triglyceride, tributyrin, was selected as a model system, and gel permeation chromatography was used to effect their separation. The irradiation treatment was conducted under vacuum at 50 Mrad. Radiolytic products were collected by a precolumn technique for the highly volatile compounds; a combination of cold finger distillation and gel permeation for the less volatile fractions and finally gel permeation chromatography of the residue after distillation for the higher molecular weight compounds. A large number of compounds expected on the basis of previous work were identified in the present work from irradiated tributyrin. In addition, the techniques employed permitted the identification of several new compounds. These include butanetriol triesters, erythritol tetraesters, and other polyglycol polyesters.     

天然产物纯度鉴定方法

天然产物产量小和结构复杂的特点,决定了其在进行结构研究之前,必须要确定化合物纯度。文章通过讨论熔点（mp）、薄层层析（TLC）、纸层析（PC）、气相色谱（GC）、高效滚相色谱（HPLC）、氢核磁共振（IHNMR）和碳核磁共振（13CNMR）的在纯度鉴定方面的特点。文章说明每一种鉴定方法有其优点,也有其不足之处,在研究过程中为了证明某个化合物纯度到达测试要求,要多试验几种纯度鉴定方法。     

Combustion and pyrolysis of poly(ethylene terephthalate). I. The role of flame retardants on products of pyrolysis

The products of pyrolysis of untreated and flame-retarded poly(ethylene terephthalate) (PET) have been studied at two temperatures using a flash pyrolysis/gas chromatography technique. The pyrolysis products were identified by gas chromatography/mass spectrometry and reaction mechanism for their formation are proposed. A quantitative and qualitative analysis of these products reveals that the phosphorus-only flame retardants have no effect on the solid-phase pyrolysis of PET. The two bromine-containing flame retardants, however, while capable of influencing the pyrolysis, were not capable of producing large changes in the major products. Their main role in the pyrolysis appears to alter slightly the balance of several competing secondary pyrolysis reactions.     

Spaltprodukte bei der verarbeitung von phenol-formaldehyd-formmassen

During the processing of phenol-formaldehyde-molding compounds with asbestos or wood fiber flour as fillers besides about 98% water low molecular phenolic cleavage products are formed. They were identifided by thin layer chromatography, gas chromatography, and HPLC as phenol, m- and o-cresol, several dimethyl-phenols, and 2- and 4-hydroxybenzylalcohol.     

Development of a Pyrolysis-Gas Chromatographic Method for characterization of plastic-bonded explosives

As part of a program to develop chemical tests which can be used to complement existing tests for mechanical properties, propellant ballistic performance, and explosive sensitivity, a detailed experimental procedure is presented for analysis of plastic-bonded explosives (PBX's) by the coupled method of pyrolysis-gas chromatography (PyGC). The method involves grinding the cooled PBX, pressing a controlled quantity on a pyrolysis wire, performing Curic-Point pyrolysis, and detecting the products after separation by gas chromatography. PyGC results are presented to show the capability of the method to differentiate aged and unaged samples of PBX's and to differentiate stabilized and unstabilized PBX's based on RDX. Also included are results from several series of reproductibility studies, which suggest that the method may require only minor modifications before it can be implemented for regular screening of these complex formulations.     

Kinetics of oxidation of 2-methylpropene over chlorine modified copper oxide catalyst

The vapour phase air oxidation of 2-methylpropene to methacrolein over a copper oxide catalyst supported on pumice, modified by a continuous supply of chlorine, was investigated in an isothermal integral flow reactor at atmospheric pressure between 300 and 450 °C. The effects of several variables, weight ratio of modifier (CI) to 2-methylpropene in the feed, feed ratio of oxygen to 2-methylpropene, reaction temperature and the reciprocal of space velocity on the conversion and product distribution were determined by gas chromatography. The results indicate that the promotional effect of the modifier is mainly due to successful suppression of further oxidation of aldehyde to undesired products. Though several mechanisms were postulated, the rate of reaction was most satisfactorily correlated by a mechanism, which assumes the rate controlling step to be the surface reaction between charged adsorbed 2-methylpropene and oxygen.     

Bilanz der Schnellpyrolyse des Rohmontanwachses

Rapid Pyrolysis of Raw Montana Wax Raw montana wax from Slovakian Lignite was subjected to rapid pyrolysis at a temperature of 600° and 700° C. The products of pyrolysis were segregated into a solid, a liquid and highly volatile fraction. The products of pyrolysis were determined in each fraction. Both the pyrolysis products as well as the original wax were fractionated by column chromatography. The individual eluates were analyzed by gas chromatography and mass spectrometry.     

Analysis of the volatile combustion products of vinyl plastics

The extensive use of plastics for insulation and building materials has created interest in the possible toxicity of their combustion products. Three poly(vinyl chloride) homopolymers, a vinyl chloride-vinyl acetate copolymer, and formulations of two of the homopolymers and the copolymer have been examined to determine the composition and toxicity of their combustion products. Differential thermal analysis and thermal gravimetric analysis were used to study the breakdown process which occurred in several steps, the largest and first being the release of hydrogen chloride from the polymer at about 300°C. Approximately 50 products of combustion were then determined qualitatively by using either infrared spectroscopy or a combination of gas chromatography and mass spectroscopy. Quantitative analyses were carried out on 22 of the combustion products, and quantitative changes with varying air supply, temperature, and heating rate were determined. A comparison of the products of the polymers and their formulations is given.     

Biotransformation of saturated monohydroxyl fatty acids to 2-tetrahydrofuranyl acetic acid derivatives: Mechanism of formations and the biological activity of 5-n-hexyl-tetrahydrofuran-2-acetic acid

Transformation of 12-hydroxyoctadecanoic acid (12-HOA) to 5-n-hexyl-tetrahydrofuran-2-acetic acid (5-HTFA) byBacillus lentus NRRL B-14864 (B-14864) was carried out in the presence or absence of oligomycin, 2-bromooctanoic acid (2-BA), or sodium azide. In addition, several saturated and monounsaturated monohydroxyfatty acids, saturated monooxofatty acids, and monounsaturated fatty acid were used as substrates for transformation reactions by B-14864 or corynebacterium FUI-2. Methyl esters of the transformation products were analyzed by gas chromatography and gas chromatography/mass spectroscopy. Various γ-lactones and tetrahydrofuran fatty acid derivatives were conversion products when saturated monohydroxyfatty acids were used as substrates; the production of 5-HTFA from 12-HOA by B-14864 cells was completely inhibited in the presence of high concentration of oligomycin, 2-BA, or sodium azide; and fatty acid β-oxidation metabolic intermediates, 6-hydroxydodecanoic, 4-oxododecanoic, and 4-oxodecanoic acids were products when 12-HOA, 10-oxo-, and 12-oxooctadecanoic acids were used as substrates. Our results suggest that the production of 5-HTFA from 12-HOA by B-14864 was through the fatty acid β-oxidation pathway. Three-day-old driedfruit beetle pupae were topically treated with 5-HTFA to test for juvenile hormone activity, and 5-HTFA was found to possess juvenile hormone-like activity in pure form but not when it was diluted to 10%. Presented in part at the 37th West Central States Biochemistry Conference Annual Meeting, Columbia, Missouri, Oct. 1994.     

Untersuchungen zur Thermischen Umsetzung von Phenylcyclopentan, -hexan, -heptan und -octan in der Gasphase

Studies on Thermal Conversion of Phenyleyclopentane, -hexane, -heptane, and -octane in the Gas Phase The title compounds were pyrolyzed from 700 to 780°C in a metallic laboratory tubular reactor in the presence of steam. The reaction products were analyzed by gas chromatography and by a combination of gas chromatography and mass spectrometry. From the phenylcyclanes tested, more than 65 hydrocarbons could be detected in the liquids, besides gaseous reaction products. In most cases unambiguous structures could be derived by using different analytical methods. As typical initial-step products phenylcyclenes, ω-phenyl-1-alkenes and 1-phenyl-1-alkenes are formed by dehydrogenation and isomerization of the title compounds. The detection of phenylalkenes corresponds well with the isomerization of unsubstituted cyclanes to the corresponding α-olefines described in former papers.     

Lecithins and lysolecithins of wheat flour

Lecithin and lysolecithin from the bound lipid of Thatcher wheat endosperm were separated and purified by column and thin-layer silicic acid chromatography. Lecithin was hydrolyzed with phospholipaseA (Crotalus adamanteus) and the products isolated and purified by silicic acid chromatography. The fatty acid composition of the original lecithin and lysolecithin and of the hydrolysis products was determined by gas-liquid chromatography. The fatty acids in the beta position of the lecithin were found to be almost entirely unsaturated, whereas those in the alpha position were saturated and unsaturated in nearly equal amounts. The differences between the fatty acid composition of the original lysolecithin and that of the lysolecithin obtained by hydrolysis of lecithin with phospholipaseA suggested the presence of both alpha and beta acyl species in the naturally occurring lysolecithin. Contribution No. 48, Food Research Institute, Research Branch, Canada Department of Agriculture, Ottawa, Canada.     

Synthesis of poly (γ‐benzyl‐L‐glutamate) with well‐defined terminal structures and its block polypeptides with alanine,leucine and phenylalanine

The ring‐opening polymerization of γ‐benzyl‐L ‐glutamate N‐carboxyanhydride (BLG‐NCA) was initiated by n‐hexylamine in N,N‐dimethyformamide under normal pressure at 0 °C. The products were characterizated by gel permeation chromatography, matrix‐assisted laser desorption/ionization time of flight mass spectroscopy (MALDI‐TOF MS), nuclear magnetic resonance etc. MALDI‐TOF MS gave direct evidence that the side reactions during the polymerization of BLG‐NCA could be greatly reduced by decreasing the reaction temperature, e.g. from room temperature to 0 °C. As a result, over 90% of the products were amino‐terminated poly(γ‐benzyl‐L ‐glutamate) (PBLG) with low polydispersity index when the polymerization was carried out at 0 °C, which could be used to re‐initiate the polymerization of other NCAs. Then several well‐defined PBLG‐containing block copolypeptides were successfully synthesized in a convenient way. Copyright © 2012 Society of Chemical Industry     

Photosensitized oxidation of methyl linolenate. Secondary products

Previous studies of secondary oxidation products by high-pressure liquid chromatography (HPLC) of autoxidized methyl oleate, linoleate and linolenate and photosensitized-oxidized linoleate are extended to photosensitized-oxidized linolenate. Photosensitized-oxidized linolenate was fractionated by silicic acid chromatography with diethyl ether/hexane mixtures. Selected silicic acid chromatographic fractions were separated by polar phase HPLC and characterized by thin layer and gas liquid chromatography and by ultraviolet, infrared, nuclear magnetic resonance and mass spectrometry. Secondary products from the photosensitized oxidation mixtures (containing 8.2 to 29.0% monohydroperoxides) included keto- and epoxy-dienes (0.4–1.6%), hydroperoxy epidioxides (0.8–4.9%), hydroperoxy bicyclic monoenes (0.1–0.3%), dihydroperoxides (1.0–5.6%), and hydroperoxy bisepidioxides (0.7–1.6%). Some of these secondary products are new and unique to photosensitized oxidation. Cyclization of the 10-, 12-, 13- and 15-hydroperoxides of linolenate would account for their lower relative concentration than that found for the 9- and 16-hydroperoxides. Dihydroperoxides may be derived from monohydroperoxides by singlet oxygenation or free radical oxidation. The hydroperoxy bis-epidioxides may be formed by further serial cyclization of the hydroperoxy epidioxides from 10- and 15-monohydroperoxides. Dihydroperoxides, hydroperoxy epidioxides and hydroperoxy bis-epidioxides are suggested as important flavor precursors in oxidized fats. The mention of firm names or trade products does not imply that they are endorsed by the US Department of Agriculture over other firms or similar products not mentioned.     

Dimers formed in oxygenated methyl linoleate hydroperoxides

The formation of dimers was demonstrated in methyl linoleate hydroperoxides decomposed by bubbling with dry air at 30 C. The dimer fraction isolated by gel permeation chromatography was further fractionated by successive silicic acid column and high performance liquid chromatography. Major components were analyzed after derivatizations by gas chromatography-mass spectrometry with several ionization methods, i.e., electron impact, chemical ionization and field desorption. After aeration for 90 min, 1.4% of the hydroperoxides were decomposed. However, almost all of the secondary products were dimers, while polar monomeric and low molecular products were negligible. After aeration for 390 min, both polar monomeric (5.0%) and low molecular (0.8%) compounds formed, but dimers and polymers (18.1%) were still the major products. These results show the importance of polymerization in the aerobic breakdown of hydroperoxides. The dimers isolated from hydroperoxides aerated 90 min could be separated into two fractions according to their polarities. The dimers identified usually were composed of octadecadienoate and oxygenated octadecenoate moieties crosslinked through either ether or peroxy linkages across C-9 or C-13 positions. The oxygen-containing functional groups found in the dimers include hydroperoxy, hydroxy and oxo groups. The polar dimers had two of these groups per molecule, while the less polar dimers had one. The main constituents of dimers were linked through peroxy bridges and found to be similar to the dimers previously identified in autoxidized methyl linoleate. These dimers are suggested as important intermediates in linoleate oxidation and as precursors of flavor deterioration.     

Pyrolysis of saturated triglycerides

Saturated monoacid triglycerides were pyrolyzed in a flowing atmosphere of helium at 630–650 C, and the products were colleted at low temperature. They were fractionated by thin layer chromatography, according to polarity, and were further resolved and analyzed by gas chromatography, mass spectrometry and IR spectrometry. Alkanes, alkenes, ketones, esters, free acids and cyclic products were identified. Among the latter are probably lactones and substituted dioxanes and dioxolanes, for which structures have been postulated. The parent acid of the triglyceride and the cyclic residual products, after loss of one acid group from the triglyceride, were prominent products. Many products of pyrolysis had structures similar to the major ions produced in the mass spectrum of the triglyceride.     

Monitoring of degradation of thermally aged nylon 6,6. II. Pyrolysis–gas chromatography

Pyrolysis–gas chromatography was used as an analytical method to evaluated the extent of chemical changes that occur in aged yarns and to demonstrate any correlation between measured physical properties and pyrolysis products. Nylon 6,6 yarn samples (2.5–3.0 mg) that were control-degraded as a function of humidity, temperature, and time were pyrolyzed at 500°C and chromatographed on a Graphpac AT-1000 column. The peak heights of pyrolysis products unique to the degraded material were correlated with measured tensile strength loss (?5 to ?75%) of the yarns. Linear relationships were found for several of the products, one of which was identified as caprolactam. Significant changes in the pyrograms were observed in nylon with tensile strength losses of 5% or less.     

Hydrothermal Treatment of Carboxy‐methyl Cellulose Salt: Formation and Decomposition of Furans,Pentenes and Benzenes

Carboxymethyl cellulose salt as a model compound was treated hydrothermally to understand the degradation and formation of several chemicals (furfural, 5‐(hydroxymethyl)‐furancarboxaldehyde, and benzene derivatives) that might be interesting as platform chemicals or fuels. To realize a manageable control, closed quartz capillaries were chosen as reactor. Experiments were conducted at temperatures from 250 (subcritical water) to 450 °C (supercritical water) and reaction times from 1 to 60 min. By studying the gas chromatography‐mass spectrometry analysis results of the liquid products, their formation and degradation were detected. It was observed that certain substances only appear for several minutes and are then degraded, while for others the concentration increases at lower rate and keeps stable even for long reaction times. The formation of several benzoic structures from a non‐ring‐structured precursor showed that different reaction mechanisms are involved. Different reaction temperatures showed good correlation to the formation rate of several substances.     

Voltammetric, chromatographic and mass spectral elucidation of the redox reactions of 1-hydroxypyrene occurring at a screen-printed carbon electrode

The electrochemical oxidation of 1-hydroxypyrene (1-OHP) has been studied at a screen-printed carbon electrode (SPCE), by cyclic voltammetry and bulk electrolysis. Cyclic voltammograms exhibited two quasi-reversible pairs of peaks (designated 1a′/1c and 3a/3c) generated from the oxidation of the parent molecule. The nature of the redox reactions were further investigated by observing the effect of scan rate and pH on the voltammetric behaviour; the results suggested that the oxidation reactions giving rise to peaks 1a and 2a involved electrochemical-chemical-electrochemical (ECE) and EECE processes, respectively. Additional studies were carried out by HPLC and GC/MS and the results strongly indicated that the oxidation products were a mixture of several pyrene-quinones. In addition, liquid chromatography/mass spectroscopy (LC/MS) investigations showed that 1-OHP had undergone oxidation reactions to produce several dimers.     

Thermal oxidative degradation of poly(4-methyl-1-pentene). I. Identification of products and mechanisms

Isotactic and atactic poly(4-methyl-1-pentene) powders were degraded in the presence of pure oxygen at temperatures of 145° and 175°C. The functional groups present in the nonvolatile products were identified using infrared spectroscopy. The volatile products that formed were identified by means of a relativly new technique which combines gas chromatography and mass spectroscopy. In this study, seventeen volatile products were detected and identified and their relative abundance estimated. The results obtained could readily be reproduced. Various oxidation mechanisms for these products are postulated.