ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Regioselectivity in the Gas-Phase Nucleophilic Attack on O-Protonated 3-Methyl-2-cyclohexen-1-ol and 1-Methyl-2-cyclohexen-1-olGas-Phase Acid-Induced Nucleophilic Displacement Reactions, Part 11, Part 10: G. Renzi, A. Lombardozzi, E. Dezi, A. Pizzabiocca, M. Speranza, preceding paper in this issue. (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 323-334 
    Details
    ISSN: 0947-6539
    Keywords: cyclohexenols ; elimination reactions ; gas-phase chemistry ; mechanistic studies ; nucleophilic substitutions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Our radiolytic study of the occurrence in the gas phase of concerted SN2′ reactions on several open-chain allylic oxonium ions generated in the gas phase from the attack of gaseous GA+ acids (GA+=CnH+5 (n = 1, 2), iC3H+7, and (CH3)2F+) on suitable substrates is now continued with cyclic allylic alcohols, such as 3-methyl-2-cyclohexen-1-ol (1) and 1-methyl-2-cyclohexen-1-ol (2), with both MeOH and NMe3 as neutral nucleophiles. With MeOH as the nucleophile, the substitution reaction exclusively takes place on 1 as the starting compounds, whereas when the substrate is 2 it is accompanied by extensive elimination. With NMe3, only the elimination reaction is observed in the same systems. The analysis of the isomeric distribution of the substitution and elimination products allows definition of the corresponding reaction patterns. As for open-chain oxonium ions, the nucleophilic attack on O-protonated 1 and 2 is preceded by significant intramolecular interconversion. Partial unimolecular dissociation of the same ionic intermediates also takes place. After careful evaluation of the extent of these side processes, it is demonstrated that the O-protonated 1 undergoes the concerted SN2 process with MeOH almost exclusively (≥ 99%). With O-protonated 2, how ever, the concerted SN2′ pathway (84-95%) prevails over the classical SN2 one (6-17%). Concomitant [1,2] (E2) and [1,4] elimination (E2′) pathways involve attack of the selected nucleophiles on the oxonium ions from 1 and 2. Their relative extent (E2′/E2:1.78-1.96 (1); 1.43-1 70 (2)) appears only slightly dependent on the nature of the ionic substrate, the nucleophile (whether MeOH or NMe3), and the leaving group (whether H2O or MeOH). The effects of both intrinsic structural factors and experimental conditions in determining the SN2′/SN2 and E2′/E2 branchings in the selected oxonium ions is discussed and compared with related gas-phase data.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19960020314
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Gas-Phase Acid-Induced SN2′ versus SN2 Mechanism in Allylic AlcoholsGas-Phase Acid-Induced Nucleophilic Displacement Reactions, Part 10. Part 9: ref. [1]. (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 316-322 
    Details
    ISSN: 0947-6539
    Keywords: allylic alcohols ; gas-phase chemistry ; ions ; mechanistic studies ; nucleophilic substitutions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A first demonstration of the existence of the concerted SN2′ mechanism in the gas phase was obtained by establishing the regioselectivity of the attack of a neutral nucleophile, such as MeOH, on several allylic oxonium ions. These were generated in the gas phase by the reaction of radiolytically formed GA+ acids (GA+=CnH+5 (n = 1, 2), iC3H+7, and (CH3)2F+) with trans- (1) and cis-2-buten-1-ol (2) as well as with 1-buten-3-ol (3). Firm evidence in favor of the concerted SN2′ pathway accompanying the classical SN2 one in these systems was obtained after careful evaluation of the extent of conceivable intramolecular isomerization both of the primary oxonium ions from GA+ attack on 1-3 before nucleophilic displacement by MeOH and of their substituted intermediates before neutralization. The intermediacy of free allylic ions in the nucleophilic substitution was ruled out by generating the ions by protonation of 1,3-butadiene and by investigating their behavior in exactly the same media employed in the substitution reactions. The regioselectivity of MeOH with the ionic substrates investigated showed the occurrence of nearly equally extensive SN2′ and SN2 pathways in the oxonium ions from 1 (SN2′ (57 ± 2%) and SN2 (43 ± 2%)) and 3 (SN2′ (54 ± 2%) and SN2 (46 ± 2%)), whereas, with 2, the SN2 (66 ± 2%) reaction prevailed over the SN2′ one (34 ± 2%). The role of intrinsic structural factors in determining the SN2′/SN2 branching in the selected oxonium ions is discussed.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19960020313
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    The effect of elastomeric liners on high-pressure liquid propellant combustion oscillationsThis work is supported by the Department of Defense Office of Munitions and the Department of Energy through a Memorandum of Understanding. (1995)
    Weinheim : Wiley-Blackwell
    Propellants, Explosives, Pyrotechnics 20 (1995), S. 311-321 
    Details
    ISSN: 0721-3115
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Liquid propellants are currently being investigated as an alternative to solid propellants in advanced gun designs. The use of liquids may provide advantages in the areas of safety, cost and performance. One area of concern in liquid propellant gun designs is the presence of large pressure oscillations: oscillations of ± 50% of the baseline pressure have been observed. These oscillations may result in a degradation of performance and reliability. The source of pressure oscillations and possible mitigation schemes are being studied in the Sandia Liquid Propellant Injector/Combustor. In this research device, the effect of acoustic liners on pressure oscillations in a high-pressure (128 MPa) liquid propellant spray combustor is studied for a hydroxylammonium nitrate-based propellant. In this study we investigated the effects of orientation and coverage fraction of elastomer liners on pressure oscillation reduction. Results for a range of elastomer/steel liner combinations are presented. along with an acoustic model and a correlation the data. The results indicate that: (1) linears can reduce oscillations by approximately three order of magnitude,(2) the reduction in pressure oscillation is independent of the placement of liners relative to the propellant flow, and (3) the magnitude of the oscillations can be correlated with the acoustic properties of the wall material.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prep.19950200606
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    facet.materialart.
    Unknown
    Distribución, áreas de concentración y estructura de la población del abadejo (Genypterus blacodes) (2013)
    Details
    Publication Date: 2021-05-19
    Description: The "abadejo" is one of the species that has been traditionally exploited in the Argentine Sea. Although the capture was not very important, it has been increased in the last years. In this work, the structure of the concentration areas of summer, spring and winter distribution and other biological items were analyzed, basing on the data collected during cruises effected by R/V "Walther Herwing" and R/V "Shinkai Maru" in these waters during 1978/79. Winter and spring distribution patterns showed the highest concentrations located between 41º and 48º SL, specially on the slope. Summer distribution pattern showed the concentration areas located between 43º30' and 48º30' LS shifted rather to the coast when comparing to the previous one. During the winter, in the shelf waters, two groups were distinguished structurally: one north of 42º SL and the other between 42º and 48º SL. The areas included in the first group showed only large size individuals, and the areas included in the second group were more or less constituted by individuals with sizes lower than 72 cm. These two groups were also observed during the spring and summer season, although it was found that the distribution of the second group was located between 44ºSL and 48ºSL, and between 47º30' SL and 48º30' SL in spring and summer respectively. The trophic spectrum of the "abadejo" mainly contains food species of the Pisces and Crustacea class as well as other complementary items like Molusca, Brachiopoda and Thaliacea.
    Description: Tesis (licenciatura). Realizada en el INIDEP (Instituto Nacional de Investigación y Desarrollo Pesquero- Mar del Plata, Argentina)
    Description: Unpublished
    Description: distribución geográfica
    Description: Ophidiidae
    Description: Genypterus blacodes
    Description: abadejo
    Description: estructura poblacional
    Description: alimentación
    Description: relaciones largo-peso
    Description: contenido estomacal
    Description: dietas
    Description: distribución estacional
    Keywords: Geographical distribution ; Population structure ; Feeding ; Length-weight relationships ; Stomach content ; Diets ; Seasonal distribution
    Repository Name: AquaDocs
    Type: Theses and Dissertations , Bachelor thesis
    Format: 16 p.
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 5
    facet.materialart.
    Unknown
    Aspectos biológico-pesqueros del abadejo (Genypterus blacodes) (2007)
    Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP)
    Details
    Publication Date: 2021-05-19
    Description: The kingklip is one of the species that has been traditionally exploited in the Argentine Sea. Although captures were not very important, they have been increased in the last years. In this paper, the structure of the concentration areas of summer, spring and winter distribution and other biological aspects were analyzed, on the basis of the data collected during cruises carried out by R/V"Walther Herwig" and R/V"Shinkai Maru" in Argentine waters during 1978/79. The trophic spectrum of the kingklip comprises mainly food species of the Classes Pisces and Crustacea as well as other complementary groups like Mollusca, Brachiopoda and haliacea.
    Description: Publisher permission
    Description: Published
    Description: Gadiformes, Ophidiidae, abadejo, relaciones tróficas, relaciones largo-peso, distribución por tamaño, distribución geográfica, cadena de alimentos, alimentación, estructura poblacional
    Keywords: Geographical distribution ; Population structure ; Feeding ; Food chains ; Geographical distribution ; Population structure ; Size distribution ; Feeding ; Length-weight relationships ; Food chains ; Trophic relationships
    Repository Name: AquaDocs
    Type: Journal Contribution
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...