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  • General Chemistry  (1,028)
  • Physical Chemistry  (232)
  • Wiley-Blackwell  (1,260)
  • Blackwell Publishing Ltd
  • 1990-1994  (1,260)
  • 1925-1929
  • 1990  (1,260)
Collection
Keywords
Publisher
  • Wiley-Blackwell  (1,260)
  • Blackwell Publishing Ltd
Years
  • 1990-1994  (1,260)
  • 1925-1929
Year
  • 11
    Electronic Resource
    Electronic Resource
    Contribution of activity coefficients to the nucleophilicity of solvent components in solvent mixtures. Influence of added acetone on selectivity values, kE/kW, in ethanol-water mixtures (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 503-508 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Literature data on the change in the selectivity values, kE/kw, for several solvolysing systems in ethanol (E)-water (W) on addition of acetone were analysed. It is suggested that acetone acts as a basic cosolvent for both ethanol and water and that the change in the activity coefficients on changing the solvent composition is mainly responsible for the observed effect.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610030804
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  • 12
    Electronic Resource
    Electronic Resource
    Cross-interaction constants as a measure of the transition state structure. Part 8. Mechanism of the reaction of 2-phenylethyl benzenesulphonates with benzylamine in acetonitrile (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 545-549 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of reactions between 2-phenylethyl benzenesulphonates (2-PEB) and benzylamines in acetonitrile at 65·0°C have been studied; the mechanism was examined on the basis of the sign and magnitude of cross-interaction constants ρij and βij. In contrast to the reactions of 2-PEB with anilines in methanol, participation of the aryl-assisted pathway was negligible, with a strong indication that the reaction proceeds largely by an intermolecular SNi mechanism with a four-centre transition state (TS). The effect of substituents on the TS variation was in accord with the predictions of the quantum mechanical model.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610030808
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  • 13
    Electronic Resource
    Electronic Resource
    Solvent polarity scales. 1. Determination of ET and π* values for phosphonium and ammonium melts (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 534-544 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The solvent polarity of a series of organic salts in their molten state has been determined using the solvatochromic dyes: pyridinium N-phenolate betaine, the basis of the ET scale, and N,N-diethyl-4-nitroniline, one of the primary standards for the π* scale. Each of these dyes was dissolved in the following liquids: lithium acetate-sodium acetate-potassium acetate eutectic; ethylammonium chloride; dimethylammonium cloride; diethylammonium nitrate; ammonium trifluoracetate; tetraethylammonium acetate; tetrabutylphosphonium chloride; octyltributylphosphonium chloride; dodecyltributylphosphonium chloride; tetrabutylammonium bromide; tetrabutylphosphonium bromide; octyltributylphosphonium bromide; dodecyltributylphosphonium bromide; octyltributylphosphonium iodide; dodecyltributylphosphonium iodide; tetrahexylammonium benzoate; methyltrioctylphosphonium dimethylphosphate; and methyltrioctylammonium chloride. The ultraviolet and visible spectra were measured for each of these. In addition, data were collected as a function of temperature and in the presence of neutral and ionic additives. In general, these molten salts represent solvent polarities equivalent to moderately polar aprotic solvents such as acetone and acetonitrile. The salts with cations capable of being hydrogen bond donors gave considerably higher values, equivalent to or higher than water, the solvent with the highest value on the ET scale. These and the eutectic mixture are thought to involve specific dye-solvent interactions which cause these anomalously high values.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610030807
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  • 14
    Electronic Resource
    Electronic Resource
    Activation barriers in photosensitized pyrimidine dimer splitting (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 581-586 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Pyrimidine dimers, which form by a symmetry allowed (πs2 + πs2) photocycloaddition reaction, are subject to photosensitized cycloreversion by electron donors, such as indoles. In a linked dimer-indole system, photoinitiated electron transfer occurs intramolecularly from indole to dimer to produce a charge-separated species (dimer-.-indole+.). This species undergoes cycloreversion in competition with back electron transfer. Studies of the temperature dependence and solvent dependence of this competition have allowed the relative values of the activation parameters for the competing processes to be determined. In water (5-65°C) the free energy of activation of splitting minus that of back electron transfer (ΔΔG≠ = ΔGspl≠ - ΔGbet≠) was found to be 1·3 kcal mol-1. The enthalpy of activation difference (ΔΔH≠) was found to be 1·1 kcal mol-1 and the entropy of activation difference (ΔΔS≠) was found to be -0·51 cal mol-1 K-1. In EPA (diethyl ether-isopentane-ethanol, 5:5:2; -85 to 25°C) the value of ΔΔG≠ remained the same, but the entropy and enthalpy contributions were different (ΔΔH≠ = 0·72 kcal mol-1; ΔΔS≠ = -1·8 cal mol-1 K-1). The results have been interpreted in terms of the effect of the polarity of the solvent on the transition states for the two competing processes. Enthalpy effects retard splitting more in water than in EPA, whereas entropy effects favor back electron transfer more in EPA than in water. Potential implications of these results for the mechanism of enzymatic photocycloreversion of pyrimidine dimers in DNA are considered.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610030905
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  • 15
    Electronic Resource
    Electronic Resource
    Masthead (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990) 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610031001
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  • 16
    Electronic Resource
    Electronic Resource
    Stereochemistry and kinetics of addition of amines to acetylenic ketones (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 627-634 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reactions of a series of 3-(p-substituted phenyl)-1-phenylprop-2-yn-1-ones with piperidine and morpholine in methanol were studied and their rates measured. The products were 3-piperidino- and 3-morpholino-3-(p-substituted phenyl)-1-phenylprop-2-en-1-ones. 1H NMR spectra were used to determine the configurations of the obtained products. A good Hammett correlation was obtained with ρ values of 1·15-1·10 and 1·15-0·53 for piperidine and morpholine, respectively, which suggest a carbanionic character of the transition state. A two-step mechanism is postulated for these nucleophilic additions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610031002
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  • 17
    Electronic Resource
    Electronic Resource
    The spin delocalization substitutent parameter σJJ. 5. Correlation analysis of 19F chemical shifts of substituted trifluorostyrenes. The unresolved polar substituent parameter σmb (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 643-650 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The 19F NMR spectra of 30 substituted α,β,β-trifluorostyrenes (Y-TFSs, 1) covering a diverse range of substituents are reported and discussed. Values (δF1, δF2, Δδ3 - 1 and Δδ3 - 2) derived from the 19F NMR chemical shifts of the fluorine atoms of 1 are found to correlate very well with σI and σR0. The results of the correlations of the 19F chemical shifts with dual (σF and σR) and triple parameter (σF, σR and σα) treatments are compared. An unresolved substituent parameter σmb, is proposed for applications to systems in which the substitutent Y interacts with a multiple bond and is compared with σ+.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610031005
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  • 18
    Electronic Resource
    Electronic Resource
    Direct measurement of the relative rates of C-protonation at unsubstituted and substituted α-and/or β-positions of a pyrrole ring (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 684-686 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Direct kinetic measurements of the C-protonation rates of 1,2,5-trimethyl- and 3,4-dimethyl-pyrroles allow the first comparison of the relative kinetic proton affinities of unsubstituted and substituted positions of the pyrrole ring.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610031010
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  • 19
    Electronic Resource
    Electronic Resource
    Stereospecificity in anionic 1, 1-addition to isocyanides. A re-examination of the (H- + HN≡C) potential energy surface (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 697-702 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The potential energy surface for the addition of the hydride ion to hydrogen isocynide reported previously was re-examined. An improved energy surface was explored at the MP2/6-31 + + G** level while relative energies were estimated at the MP4SDTQ/6-311 + + G** level and corrected for zero-point vibrational contributions. The calculated results show the existence of transition structures for both cis and trans-additions of H- to the carbon end of HN≡C even though the corresponding barrier heights are small. These transition structures did not exist at a lower level of theory (HF/4-31G) employed previously.The cis addition is calculated to be favoured over the trans addition by 10 kcal mol-1. The overall addition is thus strongly stereoselective, if not purely stereospecific. This result confirms our previous analysis of the stereoelectronic effect in the addition-elimination process involving imidoyl anions as intermediates. Recent experimental work on the addition of OH- to ArN≡C is discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610031102
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  • 20
    Electronic Resource
    Electronic Resource
    Electrochemical reduction of substituted α,α,α-trifluoroacetophenones. Linear relationship between cyclic voltammetric peak potentials and Hammett substituent constants (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 723-731 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The peak potentials of substituted α,α,α-trifluoroacetophenones were measured in acetonitrile with 0·1 M tetrabutylammonium perchlorate. The cyclic voltammograms indicated an irreversible electrochemical process for the first wave (Epc1) and a partially reversible one for the second wave (Epc2) when the scan rate was slower than 100 mV s- 1. Excellent linear correlations were observed for Epc1 with σ constants (ρ = 0·526, r = 0·999) and for Epc2 with σ- constants (ρ = 0·605, r = 0·998), respectively. Therefore, unknown σ values such as -0·36 for 3, 4-ethyleneoxy can be estimated from these correlations. The mechanism of the electrode process probably involves a single electron transfer and the formation of a pinacol.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610031105
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