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  • Articles: DFG German National Licenses  (11)
  • 1975-1979  (9)
  • 1960-1964  (2)
  • 1920-1924
  • 1890-1899
  • Free radicals
  • 1
    Electronic Resource
    Electronic Resource
    Study of an asymmetric ESR signal in X-irradiated human tooth enamel (1979)
    Springer
    Calcified tissue international 29 (1979), S. 95-99 
    Details
    ISSN: 1432-0827
    Keywords: ESR ; Radiation ; Free radicals ; Enamel ; ENDOR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary An asymmetric ESR signal and an outer doublet signal centered atg=2.00 produced in human tooth enamel by X-irradiation have been studied over a temperature range from liquid helium temperature to 380° K. The line shape of the asymmetric signal for an enamel crystallite is Lorentzian at room temperature. The temperature dependence of the integrated intensity of the asymmetric signal suggests that the signal follows a singlet-triplet model with the exchange interaction of 0.022 eV. Below about 60° K the asymmetric signal becomes broad as the temperature is decreased. The ENDOR line of the asymmetric signal shows that there exists interaction between the centers and protons. The temperature dependence of the integrated intensity of the double signal is analogous to that of the asymmetric signal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02408063
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Capto-dative Substituent Effects in Syntheses with Radicals and Radicophiles [New synthetic methods (32)]Capto-dative Substitution Effects, Part 5. - Part 4: [67].Dedicated to the double anniversary: 100 years Wurster's salts and 50 years Paneth's radical reactions with mental mirrors (1979)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 18 (1979), S. 917-932 
    Details
    ISSN: 0570-0833
    Keywords: Donor-acceptor systems ; Substituent effects ; Free radicals ; Radicophiles ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 100 yers old Wurster's salts have long been recognized as compounds with redical cations. Their unusual stabilization derives partly form capto-dative (cd) substitution. This principle is now discussed as one factor of radical stabilization and it is applied to simple methine derivatives. cd-Substitution has synthetically useful applications: cd-substituents on a carbon atom allow its selective dehydrodimerization. Olefines with geminal and thus cross-conjugated cd-substituents are “radicophilic” and permit twofold carbon radical addition. cd-Substituted olefines are useful antioxidants, polymerization inhibitors and are promising agents in the control of biological radical reactions. Generally, many reactions of cd-substituted molecules appear to involve radicals.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197909171
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Anchimerically Accelerated Bond Homolyses (1979)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 18 (1979), S. 173-180 
    Details
    ISSN: 0570-0833
    Keywords: Homolysis ; Free radicals ; Anchimeric effect ; Neighboring-group effects ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Radical reactions of the type R1—a—b—R2→•a—b—R1 + •R2 are feasible if the new bond formed between b and R1 is considerably stronger than the old bond between a and R1. Furthermore, both the radical fragments formed must be resonance stabilized. An example of this reaction type is the thermolysis of benzyl trimethylsilylmethyl ethers, in which the trimethylsilyl group (with empty orbitals) migrates to the oxygen atom (with lone pairs). Assumption of a cyclic reactive intermediate with pentacoordinated silicon explains the observed intramolecular nature and the negative entropy of activation of such homolyses.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197901733
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  • 4
    Electronic Resource
    Electronic Resource
    Paramagnetic and crystallographic effects of low temperature ashing on human bone and tooth enamel (1978)
    Springer
    Calcified tissue international 25 (1978), S. 99-104 
    Details
    ISSN: 1432-0827
    Keywords: Low temperature ashing ; Enamel ; Bone mineral ; Gas trapping ; Free radicals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Low temperature ashing by excited gas (LTA) causes crystallographic and paramagnetic alterations of the human bone and tooth enamel mineral. On the one hand, LTA induces variations of thea lattice parameter. These variations depend upon the nature of the gas used, but are little affected by its degree of excitation. Trapping of gas molecules in the crystal structure is demonstrated. On the other hand, LTA produces two preponderant paramagnetic centers in bone and enamel samples at 20°C. Their inorganic origin is clearly indicated. One of the two radicals has been identified as O3 − (g1=2.002, g2=2.010, g3=2.016) and the other as CO 3 3− (g‖=1.996, g⊥=2.003). Variations of thea lattice parameter and trapping of paramagnetic gas species do not seem to be directly related.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02010757
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Mineral substance of bone tissue and of experimental cutaneous calcinosis in rats: Chemical analysis and ESR study (1978)
    Springer
    Calcified tissue international 26 (1978), S. 259-265 
    Details
    ISSN: 1432-0827
    Keywords: Bone mineral ; Calciphylaxis ; Calcinosis ; ESR ; Free radicals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The evolution of the mineral constituents of subcutaneous calcinosis induced in rats by topical calciphylaxis was studied by the method of quantitative chemical analysis, and after treatment with excited gases by electron spin resonance (ESR) analysis. Chemical data show that the genesis of the subcutaneous calcinosis does not significantly alter the concentration of Ca, P, F, CO3, Mg, and Fe in the mineral phase of the femoral bone of calciphylactic rats. In the calcinosis an important increase of the fluoride concentration is noticed in function of the time after challenging. There is also a high concentration of Mg2+ ions in the early stages of the experimental calcification. Iron injected for the challenging is continuously present in the calciphylactic tissue after this treatment. This suggests that subcutaneous calcinosis might be a means of fixing certain heavy metal ions. After treatment with excited gases, the proportions of the trapped CO3 3− and O3 − radicals are of the same order of magnitude in calciphylactic tissue after 12 days and observations in bone mineral. These suggest that after 12 days the mineral of the calciphylactic tissue has a crystalline state close to that of bone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02013268
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Measurements of free radicals in the atmosphere by matrix isolation and electron paramagnetic resonance (1978)
    Springer
    Pure and applied geophysics 116 (1978), S. 530-536 
    Details
    ISSN: 1420-9136
    Keywords: Electron paramagnetic resonance ; Free radicals ; Matrix isolation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract With some special adaptations the technique of matrix isolation followed by detection through electron paramagnetic resonance (EPR) can also be used for the measurement of atmospheric radical concentrations. A light weight cryogenic sampling device has been constructed. It uses condensation of atmospheric CO2 or H2O at 77 K for matrix formation and trapping of the radicals. The sampler has been flown on a balloon for stratospheric sampling. First data on stratospheric, HO2 and NO2 at 32 km altitude have been obtained on a flight on 8 August 1976 and will be reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01636905
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  • 7
    Electronic Resource
    Electronic Resource
    Radiation induced free radicals as molecular probes in synthetic apatites (1978)
    Springer
    Calcified tissue international 25 (1978), S. 191-195 
    Details
    ISSN: 1432-0827
    Keywords: ESR ; Apatites ; Radiation ; Free radicals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Free radicals generated in synthetic apatitic calcium phosphates by X-ray radiation were investigated by electron spin resonance (ESR) spectroscopy. Among the species stable enough at −188° C to be identified were hydrogen atoms, phosphate radicals, and oxygen anion radicals. The ESR spectra were markedly dependent on the specific surface of the mineral. Oxygen radicals dominated the spectra of low specific surface samples while phosphate radicals were the predominant species at higher specific surfaces. Our studies suggest that the oxygen radicals are more stable in the bulk of the crystal while the hydrogen atoms and the phosphate radicals are stabilized at or near the crystal surface. It was concluded that the surface species are potentially capable of serving as probes of biologically relevant mineral-organic interfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02010767
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    The correct McLachlan method in free radicals and radical anions (1976)
    Springer
    Theoretical chemistry accounts 42 (1976), S. 87-90 
    Details
    ISSN: 1432-2234
    Keywords: McLachlan method ; Free radicals ; Radical anions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A recent modification to the McLachlan method is corrected. This modification, when correctly applied to odd alternant hydrocarbons, reproduces McLachlan's results instead of improving their agreement with experiment. The modification is irrelevant and erroneous for radical anions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00548294
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  • 9
    Electronic Resource
    Electronic Resource
    Aminyl Free Radicals (1975)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 14 (1975), S. 783-789 
    Details
    ISSN: 0570-0833
    Keywords: Free radicals ; Aminyl radicals ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Recent interest in aminyl free radicals, especially in their electronic structure, has led to many investigations in this area. This report reviews the main features of the generation of aminyls, their reactivity, and electronic properties.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197507831
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  • 10
    Electronic Resource
    Electronic Resource
    Intramolecular Free-Radical Reactions (1964)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 3 (1964), S. 525-538 
    Details
    ISSN: 0570-0833
    Keywords: Radical reactions ; Free radicals ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the present article an attempt is made to summarize the steric requirements and the influence of neighboring groups which determine the course of intramolecular radical reactions. Steroids are used as substrates for these reactions, since here the spatial arrangement of the ring members and the distances between substituents are largely fixed. Furthermore, intramolecular free-radical reactions are of practical importance in steroid chemistry in connection with substitution at non-activated carbon atoms. Almost all the reactions discussed begin with the formation of an oxygen radical by oxidation of an alcohol with lead tetraacetate or by homolysis of the corresponding hypoiodite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196405251
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  • 11
    Electronic Resource
    Electronic Resource
    Free Radicals and Free-Radical Reactions of Monovalent and Divalent SulfurFree-radical reactions of tetra- and hexavalent sulfur are not considered in this work. For a survey of these reactions, see [16], p. 326. (1964)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 3 (1964), S. 602-608 
    Details
    ISSN: 0570-0833
    Keywords: Free radicals ; Radical reactions ; Sulfur ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organic free radicals of monovalent sulfur have not been hitherto observed in solution or in melts. Steric hindrance and resonance stabilization, which are responsible for the stability of the triarylmethyl, diphenylnitrogen, and phenoxyl radicals, are apparently insufficient to stabilize the organic free radicals of monovalent sulfur in such concentrations that they can be detected by current physical methods. - It was only in 1963 that aminopolysulfur radicals (R2N—Sn—S·) were detected in solution, and arylsulfur radicals (Ar-S·) and phenylselenium radicals were isolated at ca. -180°C. - Organically bound sulfur can be stabilized in the free-radical state if association of the radicals is prevented by fixing in a crystal lattice (“cystine radical”), by repulsion between radical ions (sulfinium salts), or by freezing-in (arylsulfur radicals).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196406021
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