Library

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
    Nachweis von 4-Homocubyl-Carbenium-Ionen als reaktive Zwischenstufen (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 360-366 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Evidence for 4-Homocubyl Carbenium Ions as Reactive Intermediates4-(Hexafluoroisopropoxy)homocubane (6) is the main product of the thermolysis reaction of N-(4-homocubyl)-N-nitrosoacetamide (9) and of the solvolysis reaction of 4-homocubyl bromide (5) in hexafluoro-2-propanol. This is experimental evidence for 4-homocubyl carbenium ions as intermediates in both reactions. The solvolysis rate of 4-homocubyl bromide at 120°C in the same solvent (k1120°C=1.3 · 10-7s-1) by far exceeds that of 1-norbornyl bromide which does not react at a detectable rate under these conditions. According to force field calculations the strain enthalpy is increasing by as much as 66 kcal · mol-1 in the ionisation of 4-homocubyl bromide. Therefore nonclassical stabilization of the 4-homocubyl carbenium ion is postulated.
    Notes: Bei der Thermolyse von N-(4-Homocubyl)-N-nitrosoacetamid (9) und bei der Solvolyse von 4-Homocubylbromid (5) in Hexafluor-2-propanol entsteht 4-(Hexafluorisopropoxy)homocuban (6) als Hauptprodukt. Dies beweist das Auftrete von 4-Homocubyl-Carbenium-Ionen als Zwischenstufen beider Reaktionen. Die Solvolysegeschwindigkeit von 4-Homocubylbromid bei 120°C in Hexafluor-2-propanol (k1120°C = 1.3 · 10-7 s-1) ist wesentlich höher als die von 1-Norbornylbromid, dessen Solvolyse unter diesen Bedingungen nicht nachweisbar ist. Da die Ionisation von 4-Homocubylbromid nach Kraftfeldrechnungen mit 66 kcal · mol-1 Ansteigen an Spannungsenthalpie verbunden ist, wird für das 4-Homocubyl-Carbenium-Ion eine nichtklassische Stabilisierung angenommen.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831160137
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Darstellung und Fluoreszenzverhalten von 2,3,4,4a,10a,11,12,13-Octahydro-1,4a,10a,14-tetraazaviolanthron-Derivaten (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 3524-3528 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Flouorescene of 2,3,4,4a,10a,11,12,13-Octahydro-1,4a,10a,14-tetraazaviolanthron-Derivatives.The tetramethyl derivative 2 of the title compound was prepared by the condensation of neopentanediamine with 3,4:9,10-perylenebis(dicarboxylic anhydride). The spectra of absorption and fluorescence with λmax = 541 and 563 nm, respectively, show a bathochromic shift versus those of the perylene dyes. The quantum yield of fluorescence is 60 percent. The analogue condensation of the anhydride with ethylenediamine gives a perylene fluorescent dye as an intermediate which contains an amino group and may, therefore, be used in acid aqueous solutions.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831161027
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Eine einfache Synthese von 3-Methoxypyridin und seinen Analogen durch Alkylierungsreaktionen (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 2394-2397 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Simple Synthesis of 3-Methoxypyridine and of Analogues by Alkylation ReactionsSolid potassiumhydroxide in dimethylsulfoxide has high basicity but only low nucleophilicity and is used as a base for the methylation of 3-hydroxypridine (1) and of analogues with methyliodide. The reaction is not interferred by the addition of small amounts of water and gives yields of 40 percent for the reaction of 1 and up to 100 percent for analogues. The described reagent therefore may be an alternative to lithium diisopropylamide.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831160631
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Eine einfache Synthese der 5-Cyan-2-pyridincarbonsäure und ihres Amids (1984)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1259-1261 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Simple Synthesis of 5-Cyano-2-pyridinecarboxylic Acid and its AmideThe title compounds 3 and 2 (X = CN) are prepared in good yields by regioselective carbamoylation of 3-cyanopyridine in a Minisci reaction and by consecutive amide hydrolysis with amyl nitrite in HCl-saturated acetic acid. The observed regioselectivity apparently remains confined to carbamoyl and possibly acyl radicals and to - M-effect substituents in 3-position.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19841170340
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Der Nachweis eines Radikalketten-Mechanismus für die Knabe-Reaktion von 1,2-Dihydro-2-methylpapaverin (1984)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1436-1454 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Evidence for a Radical Chain Mechanism for the Knabe Reaction of 1,2-Dihydro-2-methylpapaverineA free radical chain mechanism is proposed for the Knabe reaction and the accompanying elimination reaction on account of their nonintegral reaction order and of successful inhibition experiments. 3,4-Dimethoxybenzyl radicals are the chain carrying species. Battersby's synthesis of N-methylpavine (19) from 1,2-dihydro-2-methylpapaverine (9) is dependent on the presence of formic acid as radical chain inhibitor. In the presence of inhibitors 1-benzyl-1,4-dihydro-2-methyl-isoquinolinium ions like 10 are persistent species whose chemistry can now be investigated.
    Notes: Die Knabe-Reaktion von 1,2-Dihydro-2-methylpapaverin (9) und die begleitende Eliminierungsreaktion wurden durch ihre gebrochene Reaktionsordnung und durch die Möglichkeit der Inhibition als Radikalkettenreaktionen erkannt, deren kettentragendes Radikal das 3,4-Dimethoxybenzylradikal ist. Die Synthese von N-Methylpavin (19) aus 1,2-Dihydro-2-methylpapaverin (9) ist an die Anwesenheit von Ameisensäure als Inhibitor der Radikalketten gebunden. Durch Zusatz von Inhibitoren können nun Immoniumionen 10 und analoge Verbindungen stabilisiert und ihre Chemie untersucht werden.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19841170414
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Notiz zur verbesserten Synthese und zur Thermochemie von cis- und trans-9-Decalincarbonsäure (1975)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 108 (1975), S. 370-371 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19751080148
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Der Einfluß der Substrat-Micellierung auf die Geschwindigkeit der Solvolyse von 1-Methylheptyl-methansulfonat in Dioxan-Wasser (1980)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 113 (1980), S. 2424-2429 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Influence of Substrate Micellisation on the Rate of Solvolysis of 1-Methylheptyl Methanesulfonate in Dioxane-WaterThe solvolysis rate of 1-methylheptyl mesylate in 25% dioxane-75% H2O was conductometrically determined at 35°C for varying substrate concentrations (c0 = 0.002-0.08 mol/l). The rate constant decreased with increasing concentration in a manner typical of substrate micellisation above the cmc. A phase diagram shows that in this range of concentration the system is passing from the one phase into the two phase region. The implications of this observation for the experimental background of the ion-pair SN2-mechanism proposed by Sneen in 1969 are discussed.
    Notes: Die konduktometrisch bei 35°C bestimmte Solvolysekonstante von 1-Methylheptyl-methansulfonat in 25% Dioxan-75% Wasser sinkt mit steigender Substratkonzentration (c0 = 0.002-0.08 mol/l). Ein Phasendiagramm zeigt, daß in diesem Konzentrationsbereich der Übergang vom einphasigen in den zweiphasigen Bereich erfolgt. Die Bedeutung dieser Beobachtung für die experimentellen Grundlagen des von Sneen 1969 vorgeschlagenen Ionenpaar-SN2-Mechanismus wird diskutiert.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19801130710
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Die Bildung von Semibenzolen bei der Dimerisierung von Benzyl-Radikalen (1978)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 111 (1978), S. 543-553 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Semibenzenes During the Dimerization of Benzyl RadicalsThe dimerization of benzyl radicals leads to bibenzyl (9) via αα-coupling and to instable semibenzenes via αo- und αp-coupling. The semibenzenes rearrange to bibenzyl. They are detected by 1H CIDNP NMR and can be trapped by acids as o- and p-benzyltoluenes. At 30°C the total yield of semibenzenes is 19%. The product distribution and its temperature dependence point to energetically different bimolecular complexes of benzyl radicals as product controlling intermediates.
    Notes: Bei der Dimerisierung von Benzyl-Radikalen bilden sich neben dem αα-Kopplungsprodukt Bibenzyl (9) auch instabile Semibenzole durch αo- und αp-Kopplung, die im Verlauf der Reaktion zu Bibenzyl umlagern. Sie werden anhand ihrer 1H-CIDNP-NMR-Spektren nachgewiesen. Mit Säure lassen sie sich als o- und p-Benzyltoluole abfangen. Aus der Ausbeute der Benzyltoluole wird geschlossen, daß die Dimerisierung bei 30°C zu 19% über Semibenzole verläuft. Die Produktverteilung und ihre Temperaturabhängigkeit weisen auf intermediäre energetisch verschiedene bimolekulare Benzyl-Komplexe als produktkontrollierende Zwischenstufen hin.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19781110213
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Wanderungstendenzen cyclischer, polycyclischer und methylverzweigter Alkylreste bei der Beckmann-Umlagerung (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3831-3854 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Migration Aptitudes of Cyclic, Polycyclic, and Branched Alkyl Groups in the Beckmann RearrangementsThe migration aptitudes of polycyclic bridgehead groups, cycloalkyl groups as well as of β-γ-and δ-branched alkyl groups in the Chapman variant of the Beckmann rearrangement were determined. From these data it is concluded that at transition state 2 the migrating group is not resembling a planarised carbenium ion R+, but rather a pentacoordinated carbonium ion structure. Because only small geometrical changes occur in the migrating group vertical stabilisation4) of charge at transition state is believed to have significant influence on the migration aptitudes.
    Notes: Die Wanderungstendenzen von polycyclischen Brückenkopfresten, Cycloalkylresten sowie β, γ-und -δ-verzweigten Alkylresten bei der Chapman-Variante der Beckmann-Umlagerung wurden bestimmt. Sie zeigen, daß die wandernde Gruppe im Übergangszustand 2 nicht Carbenium-Ionen-Charakter hat, sondern nach weitgehender Beibehaltung ihrer Geometrie eher einer Fünffach koordinierten Carboniumstruktur entspricht, die im Zuge der Umlagerungsreaktion vertikal stabilisiert4 werden kann.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19811141208
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Lösliche Perylen-Fluoreszenzfarbstoffe mit hoher Photostabilität (1982)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 115 (1982), S. 2927-2934 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Soluble Perylene Fluorescent Dyes with High PhotostabilityThe preparation of several 3,4,9,10-perylenebis(dicarboximides) 1 is described and their photostability quantitatively determined and discussed. It is shown, that substitution of the insoluble perylene dye pigments with tert-butyl groups causes solubility in organic solvents leading to high quantum yields of these dyes.
    Notes: Die Darstellung einer Reihe von 3,4,9,10-Perylentetracarbonsäurediimiden 1 wird beschrieben und deren Lichtechtheit quantitativ untersucht und diskutiert. Es läß sich zeigen, daß durch Einführung von tert-Butyl-Substituenten die als sehr schwerlöslich bekannten Perylen-Pigmentfarbstoffe in organischen Solventien leicht löslich werden und mit hohen Quantenausbeuten fluoreszieren.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19821150823
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...