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  • 1
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Empirical Increment System for Methyl Group Signals and Ringcurrent Effects on Proton NMR Spectra of Methyl-substituted Biphenyls36 methyl group NMR signals of 18 methyl-substituted biphenyl derivates have been analyzed by multiple linear regression analysis to derive 4,4′- and 2,2′-position substitution constants. The influence of the torsional angle Φ on the signals of o-methyl groups increases from -0.095, -0.284, -0.345 to -0.377 ppm for Φ = 58°, 77.5°, 85°, and 90°. These values are in good agreement with the theoretical ringcurrent model of Johnson and Bovey.
    Notes: Von 18 methylsubstituierten Biphenylderivaten werden 36 Methylgruppen-NMR-Signale durch multiple lineare Regressionsanalyse auf 4,4′- und 2,2′-Positions-Substituentenkonstanten analysiert. Der Einfluß des Verdrillungswinkels Φ auf die o-Methylgruppensignale steigt von -0.095, -0.284, -0.345 auf -0.37 ppm für Φ = 58°, 77.5°, 85° und 90°. Diese Werte werden am besten durch das theoretische Ringstrommodell von Johnson und Bovey wiedergegeben.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Application of mesityl Group as an N. M. R. Probe for the Determination of Anisotropy Effects due to ring Currents, I: Proton N. M. R. Spectra of Monosubstituted Derivatives of MesityleneThe splittings between 1H n. m. r. signals of the o,o′- and p-methyl groups for 40 monosubstitution products of mesitylene, bearing groups which show no anisotropy effect due to ring currents (in CDCl3 and CCl4) fall in the range between + 0.17 and -0.42 ppm and are therefore separated by a gap from the positive splitting (〉0.30 ppm) reported for aromatic ringsystems carrying a mesityl group as a substituent 10). With increasing positive charge on the substituent as well as with increasing effective size of the substituent the splitting of the methyl group signals is shifted to larger negative values. The splitting is independent of the concentration within the limits of ±0.02 ppm but shows significant solvent dependence. In CDCl3 all values are shifted on the average by -0.02 ppm with respect to the corresponding splitting observed in CCl4.
    Notes: Die Aufspaltungen zwischen o,o′ und p-Methylgruppensignalen der 1H-NMR-Spektren bei 60 MHz liegen bei 40 monosubstituierten Mesitylenderivaten mit Substituenten ohne Ringstromanisotropieeffekt (CDCl3 und CCl4) zwischen +0.17 und -0.42 ppm und sind Somit eindeutig durch eine Lücke von den positiven Aufspaltungen (〉0.30 ppm) getrennt, die bei mesitylsubstituierten Aromatenringsystemen beobachtet wurden 10). Mit zunehmender positiver Ladung des Substituenten oder zunehmender effektiver Substituentengröße tritt eine Verschiebung der Signalaufspaltung der Mesitylmethylgruppen nach größeren negativen Werten auf. Die Aufspaltung ist innerhalb ±0.02 ppm konzentrationsunabhängig, zeigt aber eine deutliche Lösungsmittelabhängigkeit. In CDCl3 sind alle Werte um durchschnittlich -0.02 ppm gegenüber den entsprechenden Aufspaltungen in CCl4 verschoben.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Application of the Mesityl Group as an NMR Probe for the Determination of Anisotropy Effects due to Ring Currents, II: Substituent Effects of p-Substituted Derivatives of MesitylbenzeneSubstituents in the sterically unefficient p-position to the mesityl group lead to a linear variation of the splitting between the o- and p-methyl group signals with π-electron charge densities in p-position of monosubstituted benzene derivatives calculated by an ab initio method or by the CNDO/2 method. Also good correlations are observed with Hammett σp-constants and the dipole moments of the corresponding monosubstituted derivatives of benzene.
    Notes: Substituenten in der sterisch unwirksamen p-Stellung zum Mesitylsubstituenten bewirken eine lineare Variation der Aufspaltung zwischen o- und p-Methylgruppensignalen mit der nach einer ab-initio-Methode oder nach der CNDO 2-Methode berechneten π-Elektronenladungsdichte in p-Stellung bei den entsprechenden monosubstituierten Benzolderivaten. Ebenfalls eine gute Korrelation wird mit Hammett-σp-Konstanten und den Dipolmomenten der monosubstituierten Benzolderivate beobachtet.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 84 (1972), S. 769-770 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 11 (1972), S. 725-726 
    ISSN: 0570-0833
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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