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1

Digitale Medien

On-line gas chromatographic analysis of light Fischer-Tropsch synthesis products (1986)

Snel, R.

Springer

Chromatographia 21 (1986), S. 265-268

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ISSN: 1612-1112

Schlagwort(e): Capillary gas chromatography ; Alumina PLOT columns ; C1−C7 hydrocarbons ; Alkenes ; Fischer-Tropsch products

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Notizen: Summary A simple gas chromatographic system has been developed for the rapid on-line analysis of light Fischer-Tropsch products. This involves a single chromatography fitted with two columns, a porous-layer open-tubular column coated with KCl deactivated alumina and a packed Porapak-Q column. The capillary column separates the 16 most common C1−C4 hydrocarbons and permits a reasonable analysis of the hydrocarbons in the C5−C7 range. The packed column is used for the separation of methane, carbon monoxide, carbon dioxide, water and methanol. Retention characteristics for the analysis on the capillary column are presented. The total analysis cycle is 30 minutes.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF02311879

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2

Digitale Medien

Oxidation of propene and 1-butene byMethylococcus capsulatus andMethylosinus trichosporium (1986)

Subramanian, V.

Springer

Journal of industrial microbiology and biotechnology 1 (1986), S. 119-127

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ISSN: 1476-5535

Schlagwort(e): Olefins ; Alkenes ; Epoxidation ; Biotransformation ; Methylococcus capsulatus ; Methylosinus trichosporium

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: Summary Methane-grown cells ofMethylococcus capsulatus andMethylosinus trichosporium readily oxidized propene and various isomers of butene to their respective epoxides. When examined in a proton NMR spectrum using tris([3-trifluoromethylhydroxymethylene]-d-camphorato), europium III derivative as an optically active chemical shift reagent, the products propylene oxide and 1,2-epoxybutane were found to contain equal amounts of both isomers. Methane-grown cells of both bacteria had considerable levels of reducing equivalents to catalyze the epoxidation of gaseous olefins. Cells depleted of reductants catalyzed the oxidation in the presence of low levels of methanol or formaldehyde with a stoichiometry of about 2:1. The rates of epoxidation of propene and 1-butene in a continuous reactor were 2–3-times that of a batch-wise reaction; the epoxidation activity, however, was lost within 3 h. The inactivation was attributed to the reactivity of the accumulated epoxides in the reactor. Propene and 1-butene oxidation by both bacteria were drastically inhibited by the respective products. Thus, the major problem in the application of microorganisms for production of epoxides from gaseous olefins is the rapid separation of the reactive products.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01569320

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3

Digitale Medien

Gas chromatographic retention indices for alkenes on OV-101 and squalane capillary columns (1986)

Boneva, S. ; Dimov, N.

Springer

Chromatographia 21 (1986), S. 149-151

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ISSN: 1612-1112

Schlagwort(e): Gas chromatography ; Retention indices ; Comparison of data ; Alkenes

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Notizen: Summary Gas chromatographic retention indices for 47 C5 to C8 alkenes on OV-101 dimethylsilicone at 50 and 70 °C were determined within a standard deviation of 0.3i.u. Data obtained on OV-101 are compared with those measured on squalane. The comparison of the retention index and dl/dT values from both columns is presented as linear regression equations with correlation coefficients greater than 0.98.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF02311743

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4

Digitale Medien

13C NMR and lanthanide-induced shifts in epoxides of Terpenes and related compounds (1986)

Schneider, Hans-Jörg ; Agrawal, Pawan K.

Chichester : Wiley-Blackwell

Organic Magnetic Resonance 24 (1986), S. 718-722

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ISSN: 0749-1581

Schlagwort(e): Epoxidation induced ; 13C NMR shifts ; Lanthanide induced shifts ; Epoxides ; Alkanes ; Alkenes ; Terpenes ; Chemistry ; Analytical Chemistry and Spectroscopy

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Based on literature data, and new measurements with both simple and complicated skeletons, it is shown that epoxidation-induced shifts (EIS) usually vary by only 〈4ppm if compared with the corresponding olefins, but by 〈9 ppm if compared with the saturated analogues. Shift differences between stereoisomers (E/Z or trans/cis) are consistent and, again, similar in epoxides and olefins. Larger variations are observed only for cyclic systems in which flexibility and conformational coupling can lead to significant conformational differences between the epoxide and olefin. Yb(fod)3-induced LIS values are regular if normalized by setting the LIS for the α-carbon atoms to 100%; these and the EIS values can be used to confirm or correct13C signal assignments.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/mrc.1260240818

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5

Digitale Medien

185-nm Photochemistry of Olefins, Strained Hydrocarbons, and Azoalkanes in SolutionDedicated to Professor Dietrich Schulte-Frohlinde on the occasion of his 60th birthday (1986)

Adam, Waldemar ; Oppenländer, Thomas

Weinheim : Wiley-Blackwell

Angewandte Chemie International Edition in English 25 (1986), S. 661-672

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ISSN: 0570-0833

Schlagwort(e): Photochemistry ; Azoalkanes ; Strained molecules ; Alkenes ; Chemistry ; General Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The possibility to excite directly at 185 nm chromophores that absorb in the vacuum-UV has stimulated increased activity during the last decade in this field of photochemistry. Whereas photochemical reactions at λ〈200 nm have been thoroughly investigated in the gas phase, only recently have intensive studies on the 185-nm photochemistry of organic compounds in solution provided new insights. Despite the high excitation energies, selective photoreactions are promoted in the short-lived singlet excited states (Rydberg photochemistry). In contrast to conventional photochemistry (λ 〉 220 nm), 185-nm irradiation preferentially results in intramolecular rearrangement, fragmentation, and isomerization reactions. Intermolecular radical couplings and abstractions as well as dimerizations (π, π*-excitation) compete minimally. Besides the straightforward denitrogenation of photoresistant (“reluctant”) azoalkanes, important applications of the short-wavelength photolysis are also found in technology (photolithography) and medicine (193-nm laser). Broadening the scope of the synthetic potential of the 185-nm photochemistry, which so far has been limited to direct cis/trans isomerizations, presents a challenge for the chemist.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/anie.198606613

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6

Digitale Medien

Eliminations from Olefins (1965)

Köbrich, G.

Weinheim : Wiley-Blackwell

Angewandte Chemie International Edition in English 4 (1965), S. 49-68

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ISSN: 0570-0833

Schlagwort(e): Elimination ; Alkenes ; Alkynes ; Chemistry ; General Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Eliminations from olefins are very often initiated by bases, and usually lead to formation of acetylene derivatives. In view of the numerous side-reactions and subsequent additions or rearrangments observed, the nature of the base used is of considerable significance. Organometallic bases are very versatile. In addition to dehydrohalogenation, dehalogenation by metals, and also thermolytic and photolytic eliminations. (e.g. the retrodiene reaction with exchange of substituents) are discussed. Elimination from low-membered cyclic olefins yields cycloalkynes having strained ring-systems, and the existence of these can be demonstrated by trapping them. The mechanisms known for β-elimination (E2, E1 and E1cB) occur also in the case of olefins; however - due to the sp2-hybridization of the carbon atoms taking part - they are realized with different rates of reaction relative to saturated compounds. α-Eliminations from olefines having aryl residues in the β-position lead to formation of arylacetylenes by rearrangement of the carbon skeleton. The mechanism of this reaction, which is known as the Fritsch-Buttenberg-Wiechell rearrangement, is discussed in considerable detail, and several variations of the reaction are considered. According to present-day knowledge carbenes are involved in α-eliminations only when both β-positions of the olefin are occupied by aliphatic substituents, or when they are occupied by aromatic residues where rearrangement to acetylenes is impossible for steric reasons (as for example with 9-chloromethylenefluorene). With organolithium compounds a number of dehydrohalogenations, which are formally β-eliminations, actually proceed via deprotonation on the halogenbearing carbon atom (α-metallation). α-Metallations are the rate-determining steps when ether is used as solvent, but proceed quickly in tetrahydrofuran even at low temperatures. Compounds of the type \documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}$\raise1pt\hbox{$〉$}{\rm C}\raise1pt\hbox{=\kern-3.45pt=}{\rm C(Li)Cl}$\end{document} may be prepared by this method and are recognized as intermediates in α-eliminations.

Zusätzliches Material: 2 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/anie.196500491

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7

Digitale Medien

New Reactions of Alkylidenephosphoranes and their Preparative Uses. Part I: The Acid-Base Character of Phosphonium Salts and AlkylidenephosphoranesParts II and III will appear shortly in this journal. (1965)

Bestmann, H. J.

Weinheim : Wiley-Blackwell

Angewandte Chemie International Edition in English 4 (1965), S. 583-587

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ISSN: 0570-0833

Schlagwort(e): Alkylidenephosphoranes ; Phosphonium salts ; Synthetic methods ; Phosphoranes ; Ylides ; Alkenes ; Chemistry ; General Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Phosphonium salts may be regarded as Bronsted acids, and alkylidenephosphoranes as the conjugate bases. Compounds of the two classes exist in equilibrium with each other. Phosphonium salts and alkylidenephosphoranes can be obtained by this “transylidation”. Other methods are also given for the preparation of members of both classes.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/anie.196505831

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8

Digitale Medien

New Reactions of Alkylidenephosphoranes and their Preparative Uses. Part II. Alkylidenephosphoranes and Halogen CompoundsFor Part I see Angew. Chem. 77,609 (1965), Angew. Chem. internat. Edit. 4, 583 (1965). Part III will appear shortly in this journal. (1965)

Bestmann, H. J.

Weinheim : Wiley-Blackwell

Angewandte Chemie International Edition in English 4 (1965), S. 645-660

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ISSN: 0570-0833

Schlagwort(e): Alkylidenephosphoranes ; Phosphonium salts ; Synthetic methods ; Phosphoranes ; Ylides ; Alkenes ; Chemistry ; General Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The reaction of alkylidenephosphoranes with compounds containing halogens can be used to prepare ylides, which can be converted in to useful products, e.g. by hydrolysis, by thermal decomposition, or by other reactions. Examples of such products are ketones including cyclic, unsaturated, and branched-chain ketones (including cyclic, unsaturated, and branched-chain ketones), carboxlic esters (including those of unsaturated, branched- chain, polyenecarboxylic, acetylenecarboxylic, and allenecarboxylic acids), and aldehydes.

Zusätzliches Material: 10 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/anie.196506451

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9

Digitale Medien

New Reactions of Alkylidenephosphoranes and their Preparative Uses IIIFor Part I, see Angew. Chem. 77, 609 (1965) Angew. Chem. internat. Edit. 4, 583 (1965); for Part II, see Angew. Chem. 77, 651 (1965); Angew. Chem. internat. Edit. 4, 645 (1965).. Alkylidenephosphoranes and Reagents Containing Multiple Bonds (1965)

Bestmann, H. J.

Weinheim : Wiley-Blackwell

Angewandte Chemie International Edition in English 4 (1965), S. 830-838

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ISSN: 0570-0833

Schlagwort(e): Alkylidenephosphoranes ; Phosphonium salts ; Synthetic methods ; Phosphoranes ; Ylides ; Alkenes ; Chemistry ; General Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: A few examples of preparatively useful syntheses using alkylidenephosphoranes and substances containing a C—N or C—C double bond are the preparations of olefins, allenes, pyran derivatives, and cyclopropane derivatives. Olefins, ketones, and monocyclic compounds can be obtained by autoxidation of alkylidenephosphoranes; α, β-dioxo compounds (including cyclicones) can be prepared by oxidation with peroxy-acids. Alkylidenephosphoranes can also be used for the synthesis of azines and Schiff bases. Of the many possibilities offered by the Wittig reaction, only the preparation of tritiated aldehydes and olefins will be considered.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/anie.196508301

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