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
Filter
  • 1980-1984  (10)
  • 1
    Electronic Resource
    Electronic Resource
    Radical processes in polymer burning and its retardation. II. An ESR study of flame retardation of polypropylene (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 1495-1508 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Qualitative and quantitative free radical transformations between polypropylene alkyl radicals, oxygen, and brominated flame retardants in the molten and gaseous phases of thermally treated samples are described. By ESR technique it has been proved that, depending on the applied pressure during pyrolysis, highly reactive peroxy radicals or less reactive radicals of the retardant are formed. For flame-retarded samples, compared with polypropylene without additives, the concentration of the primary alkyl radicals transferred from the molten to the gaseous phase is reduced by two orders of magnitude (from 7 × 1014 to 7 × 1012 spins/0.02 g), whereas the limiting oxygen index [LOI] is raised from 17-18% to 25-26%. The great variety of physical and chemical processes proceeding in molten polymer in the preflame zone and burning gaseous phase calls for use of different retardant types with a programmed release of Br and HBr with the temperature increase. The chain oxidation of the “fuel,” a product of the endothermic decomposition of polymer, determines the temperature of self-ignition according to the number of initiating alkyl and allyl radicals formed per unit time; the [LOI] index depends more on the length of the kinetic chain of propagation reactions in the stationary process of oxidation at a given pressure.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.170190620
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Radical processes in polymer burning and its retardation. I. ESR methods for studying the thermal decomposition of polymers in the preflame and flame zones (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 1475-1493 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The determination of the free radical distribution in the preflame and flame zones of a burning polymer (polypropylene) by ESR leads to the conclusion that in all phases of the burning polymer an exothermic reaction zone encloses an oxygen-free pyrolytic zone. Whereas in the molten preflame zone (250-350°C) the polymer decomposes to oligomers, dimers, monomers, and the relevant free radicals or biradicals, in the gaseous flame zone the heat transport from the hot outer surface into the surrounding pyrolytic zone leads (with an increasing temperature gradient) to a progressive formation of thermodynamically more stable decomposition products. The CH. radicals generated at 400-800°C, after rapid cooling, yield polyaromaties with delocalized free electrons and the atomized carbon and its dimers at 800-1200°C, after cooling, yield graphite sheets with localized free electrons in its defects. Free radicals and paramagnetic species are trapped (a) in the gaseous pyrolytic products of heated polymers on the surface of a rotating cryostat, (b) in burning polymer drops by quenching in liquid nitrogen, and (c) in different zones of a burning diffuse flame. The superimposed ESR signals of the paramagnetic products are then qualitatively and quantitatively analyzed.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.170190619
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Radical reactions in the coordination field of transition metals. VIIFor Part VI see Ref. 22. - H-transfer between phenolic and aryl-aminic H-donors and their radicals (1980)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 13 (1980), S. 406-416 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An ESR method for studying the mechanism of H-transfer reactions between H-donors of different reactivity (A1H, A2H…) and their free radicals (A1; A2.…) in non-polar solvents at ambient temperature is presented. The new technique is based on a pulsed initiation of various secondary phenoxy or nitroxy radicals in binary mixtures of hindered phenols, unhindered phenols, partially hindered thiobisphenols and diphenylamine, employing a high concentration of free RO2. and coordinated (CoIII)RO2. tert-butyl peroxy radicals generated in the redox-reaction of Co(acac)2 with tert-butyl hydroperoxide. The consecutive H-transfer reactions proceed to equilibrium until the most stable radicals are formed. In this way criteria are obtained for ranking the compared free and coordinated phenoxy radicals according to their relative stabilities. The secondarily generated phenoxy radicals from unhindered phenols after coordination to CoIII are stabilized and cannot take part in further H-transfer reactions.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270130605
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Radical reactions in the co-ordination field of transition metals. VIIIFor part VII see Ref. 29. - σ-phenoxy and σ-cyclohexadienoneoxy radicals co-ordinated to cobalt (III) and their generation by tert-butylperoxy radicals or by molecular oxygen complexed to cobalt (1980)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 14 (1980), S. 109-119 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formation of a ternary complex between phenols, Co (II)-acetylacetonate and molecular oxygen has been established at ambient temperature and in non-polar solvents. After intramolecular electron transfer the transient radical enhances the homolytic scission of the —O—H bond of the complexed phenol. The low g value of the observed ESR spectra, the net spin delocalization to the cobalt nucleus and the interaction of the unpaired electron with only a limited number of benzene ring protons, indicate the presence of co-ordinated s̰-phenoxy radicals generated from unhindered phenols (g = 2.0006 ∼ 1.9997) and of co-ordinated s̰-cyclohexadienoneoxy radicals generated from hindered phenols (g=1.9990 ∼ 1.9980). Without the cobalt-chelating acetylacetonate ligands neither the co-ordinated s̰-phenoxy nor the co-ordinated s̰-cyclohexadienoneoxy radicals can be prepared, whereas co-ordinated π-tert-butylperoxy radicals [Co(III)BuO2·] are generated in a high concentration during the reaction of tert-butyl hydroperoxide with CoCl2 in acetone.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270140207
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Radical reactions in the co-ordination sphere of transition metals. XIIIFor Part XII see Ref. 24.Radicals derived from 4,4′- and 2,2′-Alkylidenebisphenolic Antioxidants (1982)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 19 (1982), S. 153-159 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Radical species were generated from 4,4′;- and 2,2′;-alkylidenebisphenols during oxidation with free and co-ordinated [Co(III)]RO2·Radicals. This simulates the participation of bisphenolic antioxidants in the process of stabilization of hydrocarbons. Phenoxyls are primarily formed, and, depending on the character of the alkylidene bridge, some of them are gradually transformed into phenoxy radicals of the galvinoxyl type. Oxidation of alkylidenebisphenols by oxygen complexed to Co(II) yields co-ordinated cyclohexadienonyloxy radicals. The character of the alkyl substituents on the phenolic nuclei specifically influences the stability of the generated phenoxy radicals at the applied temperature. The ESR characteristics of the primarily formed phenoxyls, phenoxyls of the galvinoxyl type and co-ordinated cyclohexadienonyloxyls are discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270190310
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Paramagnetic products formed in the reactions of organometallic compounds. XIIFor Part XI see Ref. 1. ESR study of oxido anion substituted diaryl ketyl radicals (1981)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 15 (1981), S. 83-86 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the reactions of alkyl-substituted-benzenecarboxylic and -2-hydroxybenzenecarboxylic acids (ArCOOH) with alkyl-substituted phenyl Grignard reagents (RMgX) in the presence of nickel, ketyl radicals Ar—CO-—R are formed. The para substituents (H, Me, Et, Isopr and t-Bu) of R increase the non-equivalence of its ortho protons (a change of a2H = 0.43 mT, a6H = 0.422 mT to 0.435 mT, 0.395mT respectively, on substituting t-butyl for H at position 4). The oxido anion group originating from 2-hydroxybenzenecarboxylic acid has a strong push effect and nearly doubles the unpaired spin density on the phenyl ring R.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270150117
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Radical reactions in the co-ordination sphere of transition metals IXFor Part VIII see Ref. 1. - phenoxy and cyclohexadienonyloxy radicals derived from 2,2′-biphenyldiols and 2,2′-thiobisphenols (1980)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 14 (1980), S. 171-176 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: From a series of antioxidants comprising 2,2′-biphenyldiols, 2,2′-thiobisphenols and 2,2′-dithiobisphenol, free phenoxyls were prepared by oxidation with tert-butylperoxyls co-ordinated to Co(III) in non-polar media at ambient temperature. Both the effect of extended conjugation as a consequence of the direct bond between the two aromatic nuclei and, also, the steric effect of alkyl substituents could be observed. In the presence of free tert-butylperoxyls in excess, primary phenoxyls are transformed into cyclohexadienonyloxyls, which form stable radical complexes with Co(III). A mechanism for the formation of the cyclohexadienonyloxyls is suggested.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270140305
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Radical reactions in the co-ordination sphere of transition metals. XFor Part IX, see Ref. 1. - radicals derived from 4,4-biphenyldiols, 4,4′-thiobisphenols and bis(4-hydroxybenzyl)sulphide (1980)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 14 (1980), S. 249-255 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using the analysis of the splitting constants of the ESR spectra, factor are described which affect the stability of free phenoxyls and of phenoxyls co-ordinated on cobalt, generated by the reaction of tert-butyleperoxyls and 4,4′-biphenyldiols (1), 4,4′-thiobisphenols (2 and 5), 4,4′-dithiobisphenol 3a, the 4,4′-trithiobisphenol 3b, di(3,5-di-tert-butyl-4-hydroxybenzyl) sulphide (4a) and its corresponding sulphoné (4b). Phenoxy radicals are formed from compounds of type 1-4 in the presence and in the absence of oxygen. In the case of generation with oxygem complexed to cobalt, compounds 4, for steric reasons, form co-ordinated radicals of the cyclohexadienonyloxyl type. Free phenoxyls are also formed from 2a-2c, 3a and 3b as a result of the direct transfer of electrons from the sulphur non-bonding electron pair to the peroxidic bond of tert-butyl hydroperoxide in the absence of cobalt.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270140406
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    The paramagnetic species produced in the reactions of organometallic compounds XIIIFor part XII, see Ref. 1. - the anion radicals of carboxylates (1981)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 17 (1981), S. 74-76 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the reactions of meta- and para-alkyl substituted benzoic acids with aryl Grignard reagents, in tetrahydrofuran solutions and in the presence of nickel salts, the ESR spectra of the anion radicals of carboxylates derived from the benzoic acids were observed which represent the intermediates in the formation of ketyl radicals.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270170118
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Radical reactions in the co-ordinated sphere of transition metals. XIVFor Part XIII: see Ref. 20. - spin distribution of phenoxy radicals generated from biphenyldiols (1982)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 20 (1982), S. 205-211 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The phenoxy radicals obtained from 2,2′- and 4,4′-biphenyldiols show, in nonpolar solvents, symmetrization of the unpaired electron spin density on the two phenyl rings in the temperature range 290-410 K. Below 270 K the paramagnetic systems became diamagnetic. This para-diamagnetic conversion with temperature is reversible. According to INDO calculations the symmetrization of spin density is due to the formation of dimeric phenoxy radicals. The para-diamagnetic conversion at various temperatures is explained by the reversible conversion of the radical dimer to the quinone-hydroquinone pair.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270200403
    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...