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  • 1
    Electronic Resource
    Electronic Resource
    On the Thermal Cycloisomerization of 1-Vinylnaphthalene to acenaphthene. A mechanistic D-labeling study (1994)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 336 (1994), S. 415-420 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Unlabeled 1-vinylnaphthalene (1) as well as positionally D-labeled 1 have been prepared and subjected to gas phase pyrolysis at low partial pressures of the educt compounds in nitrogen. At 700°C, 1 rearranges exclusively to acenaphthene (2). Under the conditions applied a significant H-D-exchange in the 1-vinylnaphthalene as well as in the formed acenaphthene takes place. The results obtained in this way and those resulting from pyrolysis in hydrogen (instead of nitrogen) show that despite the very high degree of dilution the high selectivity of cycloisomerization from 1 to 2 is firstly controlled by H-atom driven radical chain processes, in which the cyclization of the 2-naphthylethylradical dominates the reaction course.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19943360506
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  • 2
    Electronic Resource
    Electronic Resource
    Extent of cleaning achievable by bioremediation of soil contaminated with petrochemical sludges (1997)
    Chichester : Wiley-Blackwell
    Journal of Chemical Technology AND Biotechnology 70 (1997), S. 331-336 
    Details
    ISSN: 0268-2575
    Keywords: polycyclic aromatic hydrocarbons ; petrochemical sludge ; polluted soil ; bioremediation ; gas chromatography ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bioremediation is capable of reducing the hydrocarbon concentration of contaminated soil by 75-95% depending on the soil type, the kind of hydrocarbons and the history of the contamination. The impact of different number of petrochemical sludge applications to soil on the degree of PAH elimination was assessed. A simple and reliable extraction and gas chromatographic method was used to facilitate more rapid determination of hydrocarbon contamination in soils and sludge wastes. Its application in a model laboratory bioremediation experiment and a pilot field study were used to illustrate its practical benefits. Post-remediation persistence of sludge constituents was evaluated after a single dose sludge application in the laboratory and after seven sludge applications in the field. A relative increase in the concentration of some PAHs was detected at the end of the experiments, but their individual concentrations were reduced to suggested values for industrial soils. The remaining concentration of total hydrocarbons in soil was found to be similar in both experiments, pointing to soil organic matter adsorption capacity as the factor determining hydrocarbon elimination limits in soil bioremediation. ©1997 SCI
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    On the Thermal Cycloisomerization of Long-Chain Alkylacetylenes in the Gas Phase (1989)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 715-719 
    Details
    ISSN: 0009-2940
    Keywords: Alkyne ; Carbene ; Cycloisomerization ; Pyrolysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Über die thermische Cycloisomerisierung langkettiger Alkylacetylene in der GasphaseDie thermische Cycloisomerisierung einiger Alkylacetylene wurde in einem Laborrohrreaktor aus Quarzglas untersucht. 1-Hexin (1) wird dabei durch 1,2-H-Verschiebung und 1,5-C,H-Insertion des intermediär gebildeten Pentylidencarbens (vgl. Schema 1) in 3-Methyl-1-cyclopenten (5) umgelagert. 5-Methyl-1-hexin (2) reagiert analog; es entsteht 3,3-Dimethyl-1-cyclopenten (6). Im Gegensatz zur Bildung von in 3-Stellung methylierten Cyclopentenen aus 1-Alkinen ensteht aus 2-Hexin (3) 1-Methyl-1-cyclopenten (7). Offenbar ist die Acetylen-Vinyliden-Umlagerung nicht auf 1,2-H-Verschiebung beschränkt. Der Mechanismus der Cycloisomerisierung von Alkylacetylenen wird durch Untersuchungen mit D-markierten Alkinen bestätigt. Die Ergebnisse lassen den Schluß zu, daß die Cycloisomerisierung ohne weiteres mit dem überwiegend nach einem Radikalketten-Mechanismus verlaufenden thermischen Zerfall konkurrieren kann.
    Notes: The thermal cycloisomerization of some alkylacetylenes was investigated in a tubular quartz reactor. At 570°C 1-hexyne (1) rearranges to 3-methyl-1-cyclopentene (5) with a selectivity of about 27 by a reaction sequence including an acetylene-vinylidene rearrangement and 1,5-C,H insertion of the intermediately formed alkylidenecarbene species. 5-methyl-1-hexyne (2) behaves analogously forming 3,3-dimethyl-1-cyclopentene (6), while 2-hexyne (3) provides 1-methyl-1-cyclopentene (7) indicating that the acetylene-vinylidene rearrangement is obviously not restricted to 1,2-H shifts. The mechanism of the cycloisomerization of alkylacetylenes is investigated by means of D-labeled parent alkynes. The results show that the unimolecular cycloisomerization via alkylidenecarbenes obviously can be an important channel despite the dominance of a radical chain course.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19891220419
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  • 4
    Electronic Resource
    Electronic Resource
    Thermal Rearrangements, XXII. The Propargyl-Cope Rearrangement of meso- and d,l-3,4-Dimethyl-1,5-hexadiyne-3,4-diol (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 959-963 
    Details
    ISSN: 0009-2940
    Keywords: Rearrangements, thermal ; Propargyl-Cope reaction ; 1,5-Hexadiyne-3,4-diol ; Cyclobutene ; 3,4-diacetyl ; Fragmentations, retro-ene ; Tandem reactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal behavior of meso- and d,1-3,4-dimethyl-1,5-hexadiyne-3,4-diol (meso- and d,1-4) has been studied at 400°C in the gas phase. In a tandem reaction the diols isomerize via the bisallenes 5 first to cis- and trans-3,4-diacetylcyclobutene (cis- and trans-8) which have been detected as intermediates by 13C-NMR spectroscopy as well as catalytic hydrogenation to 1,2-diacetylcyclobutane (9). Subsequently, 8 stabilizes itself by ring opening to (E,Z)- and (E,E)-3,5-octa-dien-2,7-dione (E,Z) and [(E,Z)-6]. As a side reaction retroene cleavage of 4 to 2-butynone (10) and methyl vinyl ketone (12) is observed. By pyrolysis of the pure diastereomers 4 it is shown that the retro-ene process is more pronounced in the d,l than in the meso series.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270526
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  • 5
    Electronic Resource
    Electronic Resource
    Zur Gasphasenpyrolyse von 6-alkylierten Pentafulvenen (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 1855-1860 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Gas-Phase Pyrolysis of 6-Alkylated PentafulvenesGas-phase pyrolysis of the 6-alkylfulvenes 1-3 results in an isomerization process providing the corresponding alkyl aromatics. In addition, monocyclic aromatics with C numbers smaller than those of the starting fulvenes are formed. At temperatures 〈500°C 2 reacts almost exclusively to the isopropenylcyclopentadienes 4 and 5. At higher temperatures the isomerization to the isomeric xylenes is favored (propably on a route including the tautomeric dimethylbenzvalenes). At 575°C the resulting yield ratio of o:m:p was determined to be 1:3.7:1. Toluene is the dominant aromatic side product from 2. It is formed predominantly from 4 and 5 (which are closely connected with 2 by isomerization steps) by a radical process. Cyclopentadienylvinyl and vinylcyclopentadienyl radicals are supposed to be essential radical intermediates.
    Notes: Aus den 6-Alkylfulvenen 1-3 entstehen bei der Gasphasenpyrolyse mit hoher Selektivität die isomeren Alkylaromaten sowie Einkernaromaten mit jeweils geringeren C-Zahlen. Bei Temperaturen bis 500°C werden aus 2 nahezu ausschließlich die beiden Isopropenylcyclopentadiene 4 und 5 gebildet, Temperaturen 〈500°C begünstigen die Isomerisierung zu den isomeren Xylolen (vermutlich über die tautomeren Dimethylbenzvalene); ihr Verhältnis wurde bei 575°C zu o:m:p = 1:3.7:1 ermittelt. Toluol ist das vorherrschende aromatische Nebenprodukt aus 2. Seine Bildung erfolgt über einen Radikalprozeß vorzugsweise aus den mit 2 im Isomerisierungsverbund stehenden 4 und 5. Als Intermediate werden Cyclopentadienylvinyl- und Vinylcyclopentadienyl-Radikale angenommen.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19881211026
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  • 6
    Electronic Resource
    Electronic Resource
    Das Thermogramm einer C6H6-Chemie im Temperaturbereich von 450 bis 730°C (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1747-1753 
    Details
    ISSN: 0009-2940
    Keywords: Isomerization, thermal ; Radicals ; D-Labeling ; 1,5-Hexadiyne ; Pentafulvene ; Rearrangement, homoallyl ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermal Rearrangements, XXIII[1].  -  The Thermogram of a C6H6 Chemistry in the Temperature Range from 450 to 730°CThe thermal isomerization of 1,5-hexadiyne (1) and its [1,6-D2]-labeled derivative (1a) was studied in the temperature range 450-730°C and in the presence of different carrier gases (N2, H2, D2, N2/toluene). By detailed analysis (GC, GC MS, NMR) all volatile reaction products were identified and determined quantitatively by using hexafluorobenzene as an internal standard. The experimental data show clearly that the reaction products are formed by two different routes: (i) electrocyclization leading to dimethylene cyclobutene (3) at temperatures up to about 600°C and (ii) radical reaction leading to benzene (4) and pentafulvene (5) at temperatures above 550°C. Cyclopentadienylmethyl radicals are supposed to be the essential radical intermediates.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270926
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  • 7
    Electronic Resource
    Electronic Resource
    Über 1,2-Umlagerungen und C—H-Einschubreaktionen Acyclischer AlkylidencarbeneHerrn Prof. Dr. Dr. H. G. O. Becker zum 65. Geburtstag gewidmet (1987)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 329 (1987), S. 49-54 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On 1.2-Shift Reactions and C—H-Insertions of Acyclic Alkylidene CarbenesTwo series of acyclic terminal vinyl bromides (1…4 and 5…7) were tested in the reaction with potassium tert-butoxide as precursors of alkylidene carbenes. As expected 1 up to 4 only give 1-alkynes whereas the 2-methylated vinyl bromides 5, 6 and 7 yield 1-methylated cyclopentenes predominantly besides 2-alkynes. The formation of cyclopentenes indicates a reaction route via alkylidene carbenes and 1,5-C—H-insertion reactions, that of 2-alkynes is convincing evidence for 1,2-alkyl shift reactions in 2-methyl substituted alkylidene carbenes. The selectivity of 1,5-C—H-insertion depends on the degree of alkyl substitution of the C-5-atom. At 240°C the selectivity is 1°:2°:3° ≈ 1:54:240.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19873290107
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