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  • 1975-1979  (23)
  • 1965-1969  (11)
  • 1960-1964  (6)
  • 1920-1924
  • Catalysis
  • 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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  • 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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  • 3
    Electronic Resource
    Electronic Resource
    Triphase Catalysis [New synthetic methods (27)] (1979)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 18 (1979), S. 421-429 
    Details
    ISSN: 0570-0833
    Keywords: Triphase catalysis ; Catalysis ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Triphase catalysis (TC) has recently been introduced as a unique form of heterogeneous catalysis in which the catalyst and each of a pair of reactants are located in separate phases. Based on this concept, new synthetic methods have been developed for aqueous phase-organic phase reactions using a solid phase catalyst. Although it is only at an early stage of development, TC shows considerable potential for practical use. Our mechanistic understanding of these highly complex catalytic systems is at present very limited and detailed examination will be required before their relationship to phase-transfer, micellar, and interfacial catalysis becomes clear.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197904213
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  • 4
    Electronic Resource
    Electronic Resource
    Catalytic Reactions with Hydrosilane and Carbon Monoxide [New synthetic methods (30)] (1979)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 18 (1979), S. 837-846 
    Details
    ISSN: 0570-0833
    Keywords: C-C coupling ; Synthetic methods ; Catalysis ; Silanes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reagent hydrosilane/carbon monoxide opens up new possibilities for organic synthesis. Four cases will be discussed: 1. The reaction of olefins with hydrosilane (trialkylsilane) and carbon monoxide in the presence of Co, Ru, and Rh complexes leads to enol silyl ethers having one more carbon atom that the olefins. 2. Cyclic ethers underto carbonylative ring opening to ω-siloxyaldehydes when reacted with hydrosilane and carbon monoxide in the presence of Co2(CO)8 as catalysts 3. Aldehydes are catalytically converted into the next higher α-siloxyaldehydes or 1,2-bis(siloxy)alkenes depending on the reaction conditions used. 4. The reaction of alkyl acetates proceeds in various ways depending on the nature of the alkyl group; enol silyl ethers or alkenes are optained.-Mechanisms of these Co2(CO)8 catalyzed reactions using hydrosilane and carbon monoxide are discussed in which HCo(CO)n or R3SiCo(CO)nL function as catalytically active agents. With these species there are four types of catalytic cycles.-The synthetic possibilities of these catalytic reactions have still not been fully explored.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197908371
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  • 5
    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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  • 6
    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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  • 7
    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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  • 8
    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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  • 9
    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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  • 10
    Electronic Resource
    Electronic Resource
    Anab initio theoretical study of the binding of ZnII with biologically significant ligands: CO2, H2O, OH−, imidazole, and imidazolate (1978)
    Springer
    Theoretical chemistry accounts 49 (1978), S. 161-181 
    Details
    ISSN: 1432-2234
    Keywords: ZnII complexes (ab initio study) ; Catalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zinc is one of the most important biological metals involved in the catalytic site of many enzymes. SCFab initio computations with good quality basis sets are reported for monoadducts of ZnII with various biologically significant ligands, and the fundamental features of the binding are characterized, using in particular energy decomposition scheme, population analysis and difference density curves. A test of the possibility of using pseudopotentials in this domain is also reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00553796
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  • 11
    Electronic Resource
    Electronic Resource
    Anab initio theoretical study of the binding of ZnII with biologically significant ligands: CO2, H2O, OH−, imidazole, and imidazolate (1978)
    Springer
    Theoretical chemistry accounts 49 (1978), S. 161-181 
    Details
    ISSN: 1432-2234
    Keywords: ZnII complexes (ab initio study) ; Catalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zinc is one of the most important biological metals involved in the catalytic site of many enzymes. SCFab initio computations with good quality basis sets are reported for monoadducts of ZnII with various biologically significant ligands, and the fundamental features of the binding are characterized, using in particular energy decomposition scheme, population analysis and difference density curves. A test of the possibility of using pseudopotentials in this domain is also reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02399065
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  • 12
    Electronic Resource
    Electronic Resource
    Superacid-Catalyzed Oxygenation of Alkanes. [New synthetic methods (26)]“Oxyfunctionalization of Hydrocarbons”, Part 9. Part 8: G. A. Olah, R. Ohnishi, J. Org. Chem. 43, 865 (1978). (1978)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 17 (1978), S. 909-931 
    Details
    ISSN: 0570-0833
    Keywords: Oxygenation ; Alkanes ; Synthetic methods ; Superacidic systems ; Catalysis ; Magic acid ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Owing to the ready availability of the starting materials, the functionalization of saturated hydrocarbons for preparing chemical intermediates and products represents an attractive goal. The possibility of converting alkane in a controlled way into alcohols, ketones etc., i.e. to oxyfunctionalize them, is particularly challenging. After a short account of previous methods used for the oxidation of alkanes, particular emphasis will be given to recently developed reactions of alkanes with oxygenating agents in superacidic media.
    Additional Material: 16 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197809091
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  • 13
    Electronic Resource
    Electronic Resource
    Cobalt-Catalyzed Pyridine Syntheses from Alkynes and Nitriles (1978)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 17 (1978), S. 505-515 
    Details
    ISSN: 0570-0833
    Keywords: Pyridines ; Alkynes ; Nitriles ; Synthetic methods ; Cobalt catalysts ; Catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Soluble organocobalt catalysts permit selective formation of substituted pyridines under mild conditions in a single step: mono-, di-, and trisubstituted pyridines can be obtained at will in high conversions and high yields from nitriles and alkynes. Polynuclear derivatives such as bipyridines can also be prepared by this method.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197805051
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  • 14
    Electronic Resource
    Electronic Resource
    4-Dialkylaminopyridines as Highly Active Acylation Catalysts. [New synthetic method (25)]4-Dialkylaminopyridines as acylation catalysts, 4th Communication. - 3rd Communication: G. Höfle, W. Steglich, Synthesis 1972, 619.Pyridine syntheses, 1st Communication. - 2nd Communication: H. Vorbrüggen, J. Kottwitz, K. Krolikiewicz, Chem. Ber., in preparation. This publication gives a complete survey of the various syntheses of DMAP and PPY; H. Vorbrüggen, DOS 2517774 (1975). Schering AG; Chem. Abstr. 86, 55293d (1977). (1978)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 17 (1978), S. 569-583 
    Details
    ISSN: 0570-0833
    Keywords: 4-Dialkylaminopyridines ; Amino pyridines ; Acylation ; Catalysis ; Synthetic methods ; Pyridines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 4-dialkylaminopyridines can be accomplished in two steps starting from pyridine. Compared to pyridine, these derivatives are approximately 104 times more active when used as acylation catalysts. Dialkylaminopyridines are being used with ever-increasing frequency for acylation reactions which proceed either incompletely or not at all in pyridine. This article reviews the various possible applications of 4-dialkylaminopyridines in terpene, steroid, carbohydrate and nucleoside chemistry as well as in the transformation of amino acids into α-acyl aminoketones and polymerization of isocyanates. In addition, N-substituted 4-dialkylaminopyridinium salts can be used for the transfer of sensitive groups to nucleophiles in aqueous medium. The exceptional catalytic effect of these derivatives, even in non-polar solvents, is due, in part, to the formation of high concentrations of N-acylpyridinium salts which are present in solution as loosely-bound, highly reactive ion pairs.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197805691
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  • 15
    Electronic Resource
    Electronic Resource
    Polymeric Catalysts (1978)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 17 (1978), S. 657-670 
    Details
    ISSN: 0570-0833
    Keywords: Polymeric catalysts ; Catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The present-day position in the field of polymeric catalysts is outlined. The following selected groups of polymeric catalysts are discussed: synthetic hydrolases, immobilized enzymes, phase-transfer catalysts, nucleophilically active bases, polymers with conjugated π-systems, photosensitizers, polymers as carriers for catalytically active metals or ions, and immobilized homogeneous catalysts. Polymeric catalysts have the following valuable properties: insoluble polymeric catalysts are readily separable from reaction solutions and can often be re-used without loss of activity; a hydrophobic matrix protects the organometallic active center from deactivation by oxygen and water; by fixation of finely divided metals on an ion exchanger, multistage reactions may be effected successively in one reactor. Polymeric carriers may influence the catalytic properties; for example, in the case of immobilized enzymes on polyionic carriers the pH of the activity maximum may be shifted.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197806571
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  • 16
    Electronic Resource
    Electronic Resource
    Entropy, Binding Energy, and Enzymic CatalysisBased on a lecture presented at the symposium on “Drug-Receptor and Drug-Enzyme Interactions” at Namur (Belgium) in May 1976. (1977)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 16 (1977), S. 449-459 
    Details
    ISSN: 0570-0833
    Keywords: Entropy ; Binding energy ; Enzyme catalysis ; Catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Why are enzyme-catalyzed reactions so much faster than uncatalyzed reactions, and why are enzymes so specific? What is the effect of mere approximation of enzyme and substrate, and what is the influence of the strain energy? Attempts to answer these questions have led to comparisons between entropy changes in intermolecular and intramolecular reactions, and to determinations of the intrinsic energy of the bond arising by non-covalent interaction between enzyme and substrate.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197704491
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  • 17
    Electronic Resource
    Electronic Resource
    Advances in Phase-Transfer Catalysis [New synthetic methods (20)]Phase-Transfer-Catalyzed Two-Phase Reactions in Preparative Chemistry, Part 2. - Part 1: [2]. (1977)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 16 (1977), S. 493-505 
    Details
    ISSN: 0570-0833
    Keywords: Phase-transfer catalysis ; Catalysis ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Phase-transfer catalysis (PTC) has grown into a versatile preparative method in the last few years. The most notable new developments include the use of crown ethers as phase-transfer catalysts and the introduction of solid-liquid PTC. Some representative examples have been selected from the large number of new PTC reactions and some of them are summarized in tables.
    Additional Material: 11 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197704933
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  • 18
    Electronic Resource
    Electronic Resource
    Titanium Tetrachloride in Organic Synthesis [New synthetic methods (21)] (1977)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 16 (1977), S. 817-826 
    Details
    ISSN: 0570-0833
    Keywords: Titanium tetrachloride ; Synthetic methods ; Catalysis ; C-C coupling ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Titanium tetrachloride can accelerate numerous organic reactions. Valuable syntheses of, e.g., allyl sulfides, amides, enamines, and ketones are based upon transformations of functional groups with TiCl4. Particular mention should also be made of carbon-carbon linkage with TiCl4 which permits the synthesis of hydroxy ketones and carbonyl compounds of the Michael adduct type. TiCl4 reduced in situ is suitable for the reduction of chloroarenes or the linkage of two aldehyde molecules to give an alkene.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197708171
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  • 19
    Electronic Resource
    Electronic Resource
    Efficiency and Evolution of Enzyme Catalysis (1977)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 16 (1977), S. 285-293 
    Details
    ISSN: 0570-0833
    Keywords: Evolution ; Enzyme catalysis ; Catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new function derived from kinetic data, the efficiency function, can be used to quantify the efficiency of a catalyst. For freely diffusing species the maximum efficiency is unity. The enzyme triose phosphate isomerase has an efficiency of 0.6 and is thus almost a perfect catalyst. The efficiency of the acetate ion as catalyst for the same reaction is 2.5 × 10-11. This increase in catalytic efficiency is discussed in terms of three types of evolutionary improvement: the uniform binding of the substrate to the enzyme, changes in the internal thermodynamics of the bound states, and more effective catalysis of elementary steps. These concepts are illustrated for triose phosphate isomerase.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197702851
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  • 20
    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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  • 21
    Electronic Resource
    Electronic Resource
    Detoxification of Automotive Exhaust Gases with Multifunctional Catalysts (1976)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 15 (1976), S. 586-592 
    Details
    ISSN: 0570-0833
    Keywords: Environmental chemistry ; Automotive exhaust gases ; Exhaust gases ; Catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon monoxide, hydrocarbons, and nitrogen oxides can be simultaneously transformed into inoffensive substances on multifunctional catalysts. Consisting of noble metals or base metal oxides deposited on an inert support, these catalysts can be used in monolithic form or as granular packings. Compared with other methods of automotive exhaust detoxification, multifunctional catalysts are distinguished by incurring fuel savings.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197605861
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  • 22
    Electronic Resource
    Electronic Resource
    Application of Catalyzed Reactions in Analytical Chemistry (1976)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 15 (1976), S. 150-156 
    Details
    ISSN: 0570-0833
    Keywords: Catalysis ; Analytical methods ; Trace analysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Catalyzed reactions are becoming increasingly improtant in analytical chemistry, and especially in trace analysis. The acceleration of a particular reaction (indicator reaction) promoted by the catalyst provides information about the catalyst concentration. Substances which lower or raise the activity of a catalyst (inhibitors or activators, respectively) can likewise be determined in this way. The course of a reaction is usually monitored by physical measuring techniques. Various methods of conducting these kinetic-catalytic studies are discussed in this article. - Use of catalyzed reactions for end point detection in volumetric analysis is also feasible.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197601501
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  • 23
    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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    The Catalytic Activity of Transition Metal Compounds in the Liquid-Phase Oxidation of Hydrocarbons (1969)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 8 (1969), S. 97-107 
    Details
    ISSN: 0570-0833
    Keywords: Transition metals ; Oxidation ; Hydrocarbons ; Catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The way in which dissolved transition metal compounds affect the liquid-phase oxidation of hydrocarbons is demonstrated for compounds of cobalt, copper, and manganese. Kinetic investigations on model systems and comparisons with the non-catalyzed reaction show that the catalysts participate in all the oxidation steps.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196900971
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  • 25
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    The Photolysis of Iodoaromatic Compounds (1968)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 7 (1968), S. 36-44 
    Details
    ISSN: 0570-0833
    Keywords: Photolysis ; Iodoaromatic compounds ; Dehydrobenzene ; Free radicals ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Under appropriate conditions, the photolysis of iodoaromatic compounds yields derivatives of biphenyl and phenanthrene, as well as organometallic compounds. Ring closures of o-terphenyls to triphenylenes and of benzanilides to phenanthridones are described. The formation of dehydrobenzene (benzyne) on photolysis of 1,2-diiodobenzene in solution has been established. The photolysis of various substituted iodoaromatic compounds or of substances such as CH3I, ICN, ICH3, COOH, or RC≡CI, provides a general method for the generation of a large variety of free radicals in solution. The potential uses of photochemically initiated exchanges of iodine in ArI for 131I, Li, D, Cl, or Br are noted.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196800361
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  • 26
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    Free Radical Studies at Low Temperatures (1968)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 7 (1968), S. 507-519 
    Details
    ISSN: 0570-0833
    Keywords: Radical reactions ; Free radicals ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Free radicals can be produced in the gas phase and then condensed together with the molecules of an inert gas; they can also be generated and trapped in isolated sites in rigid solids. IR and ESR spectra of trapped radicals provide information concerning their structure and chemical properties. The techniques employed for producing and studying radicals are reviewed and a number of recent IR and ESR investigations of trapped radicals are discussed. The last part of the article deals exclusively with the applications of the rotating cryostat to the study of the ESR spectra and reactions of trapped radicals at low temperatures.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196805071
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  • 27
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    Spin Density Distribution in 2,4,6-Triphenylphenoxyl (1967)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 6 (1967), S. 34-40 
    Details
    ISSN: 0570-0833
    Keywords: Spin density distribution ; 2,4,6-Triphenylphenoxyl ; Free radicals ; EPR spectroscopy ; Phenoxyl ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The distribution of the unpaired electron over the oxygen and the 24 carbon atoms in the free 2,4,6-triphenylphenoxy radical was determined by electron spin resonance spectroscopy and quantum-mechanical approximation methods. The hyperfine splitting was evaluated with the aid of the spectra of triphenylphenoxyls deuterated in some or all of the substituent phenyl groups. The results of the quantum-mechanical approximations were checked by recording the ESR spectra of triphenylphenoxyls labeled with 13C in positions 1,2,3, or 4 of the central ring. The spin density distribution permits a first discussion of the 17O-coupling constants of correspondingly labeled triphenylphenoxyl and other organic free radicals.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196700341
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  • 28
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    The Active Species in Homogeneous Ziegler-Natta Catalysts for the Polymerization of EthyleneExtended version of a lecture delivered at the “Makromolekulares Kolloquium”, Freiburg, in March 1967. (1967)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 6 (1967), S. 790-798 
    Details
    ISSN: 0570-0833
    Keywords: Ziegler-Natta catalysts ; Catalysis ; Polymerization ; Polyethylene ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cp2TiCl2 and Cp2TiEtCl (Cp = cyclopentadienyl, Et = ethyl), in combination with aluminum alkyls, have been studied as model catalyst systems for the polymerization of ethylene in toluene. The activity of these systems resides in the presence of a complex molecule involving an alkylated Ti(IV) and an alkylated Al species, linked together by chlorine bridge bonds. The environment of the Ti is of octahedral symmetry with one vacant site available for the coordination of ethylene. The bridged Al-alkyl causes a destabilization of the Ti-alkyl bond (“trans effect”), thus rendering it active for polymerization. The reduction Ti(IV) → Ti(III), inevitable in these systems, involves the irreversible change from octahedral to tetrahedral symmetry with loss of the catalytic activity. Polymerization and reduction are supposed to occur at the same catalyst site. Magnetic methods (susceptibility and EPR) as well as the kinetics of polymerization were used in the investigation of these catalyst systems.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196707901
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  • 29
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    Nickel-Catalysed Reactions of Allyl Halides and Related Compounds (1967)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 6 (1967), S. 124-133 
    Details
    ISSN: 0570-0833
    Keywords: Allyl halides ; Catalysis ; Nickel ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Allyl compounds react with carbon monoxide, or with carbon monoxide and acetylene, in the presence of tetracarbonylnickel as catalyst. These catalysts are involved also in coupling reactions and addition reactions of activated olefins and ketones. Reactions of this type can be used for the preparation of unsaturated aliphatic acids, esters, nitriles, hydrocarbons, alicyclic ketones, keto acids, keto esters, diketones, lactones, phenols, and other compounds. The reactions proceed via π-allylnickel complexes.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196701241
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  • 30
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    Applications and Limitations of Magnetic Methods in Free-Radical ChemistryDedicated to Wilhelm Klemm in memory of the work done together (1966)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 5 (1966), S. 6-15 
    Details
    ISSN: 0570-0833
    Keywords: Radical reactions ; Free radicals ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The paper describes the application and limitations of magnetic methods to the problems of free-radical chemistry (detection and quantitative investigation of the free-radical state, relationships between structure and free-radical formation, “distribution” of the unpaired electron, detection of mesomeric C, O, N, P, As, and Sn radicals, g-factors, triplet states, and hyperfine structure). The problem of the diradical is described, and the paper closes with a discussion of the “Selwood effect”.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196600061
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    Formation of Free Radicals in Polyamide Fibers during DrawingPublished on the occasion of the 100th anniversary of the establishment of Badische Anilin- & Soda-Fabrik AG., on April 6th, 1965. (1965)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 4 (1965), S. 332-335 
    Details
    ISSN: 0570-0833
    Keywords: Free radicals ; Polyamides ; Fibers ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formation of free radicals during the process of drawing of spun fibers was observed for the first time with two polyoxamides. The fibers turn red, and an ESR signal can be detected. Both, color and ESR absorption are not permanent. The decrease in the intensity of the ESR absorption and the change in the optical reflectance with time, as well as the dependence of the decoloration on temperature were investigated. The action of high-energy radiation on the polyoxamides also leads to a red coloration and gives rise to ESR signals. It is concluded that the red color is due to free radicals associated with the oxamido group.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196503321
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  • 32
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    Recent Results in the Catalytic Oligomerization and Co-oligomerization of ButadienePublished on the occasion of the 100th anniversary of the establishment of Badische Anilin- & Soda-Fabrik AG., on April 6th, 1965. (1965)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 4 (1965), S. 327-332 
    Details
    ISSN: 0570-0833
    Keywords: Butadiene ; Oligomers ; Catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A number of new catalyst systems based on transition-metal compounds have been developed for the oligomerization and co-oligomerization of butadiene. These catalysis promote dienylations and the formation of other C—C linkages, and make possible the synthesis of new open-chain and cyclic compounds from butadiene.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196503271
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    The Function of the promotors in the Technical Ammonia CatalystPublished on the occasion of the 100th anniversary of the establishment of Badische Anilin- & Soda-Fabrik AG., on April 6th, 1965. (1965)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 4 (1965), S. 341-347 
    Details
    ISSN: 0570-0833
    Keywords: Promotors ; Catalysis ; Ammonia synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An attempt is made to give a phenomenological description of the relationships between the catalytic activity and the distribution of the promotors in the reduced ammonia catalyst. Investigations were carried out on series of catalysts whose compositions were gradually brought closer to that of technical ammonia catalysts by the addition to iron of one new activator (Al2O3, K2O, CaO, MgO, SiO2) at a time.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196503411
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    The Use of Electron Paramagnetic Resonance in Organic Chemistry (1965)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 4 (1965), S. 856-867 
    Details
    ISSN: 0570-0833
    Keywords: EPR spectroscopy ; Free radicals ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The more recent applications of electron paramagnetic resonance (EPR) to organic chemistry include the investigation of triplet states, donor-acceptor complexes, short-lived free-radical intermediates, and reaction kinetics. The principles of the theoretical calculations required to obtain the maximum information from EPR spectra are outlined for free radicals containing π-electron systems. EPR intensities, line widths, hyperfine splitting, and g factors permit the determination of free-radical yields, ionic charges, rotation frequencies in rotamers, electron density distributions, electronegativities, intramolecular torsion angles, solvent effects (resulting from hydrogen bonding), and π-orbital energies. - The production of free radicals with the aid of initiation reaction in flow systems, by irradiation, and by electrolysis seems particularly promising.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196508561
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    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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    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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    Proton Transfer, Acid-Base Catalysis, and Enzymatic Hydrolysis. Part I: ELEMENTARY PROCESSESPart II (Catalytic Mechanisms) will appear shortly in this journal.Dedicated to Dr. W. Foerst on the occasion of his 65th birthday (1964)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 3 (1964), S. 1-19 
    Details
    ISSN: 0570-0833
    Keywords: Proton transfer ; Catalysis ; Enzyme catalysis ; Hydrolysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The proton occupies a special position as a promoter and mediator in chemical reactions occurring in solution. Many reactions in organic chemistry are catalysed by acids or bases; likewise, most enzymes contain active groups which promote acid-base catalysis. To understand the reaction mechanisms involved, it is necessary to identify the elementary steps as well as their course in time. Systematic investigation of these elementary steps as well as their course in time. Systematic investigation of these elementary steps has become possible only with the development of new methods for studying very fast reactions. The present paper reviews the information obtained in this type of investigation. The result is a relatively complete picture of the elementary proton transfer mechanisms and a comprehensive description of the modes and laws of acid-base and enzymatic catalysis.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196400011
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    The Mechanism of the Action of Organometallic CatalystsDedicated to Prof. Dr. Karl Winnacker on the occasion of his 60th birthday. (1964)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 3 (1964), S. 93-101 
    Details
    ISSN: 0570-0833
    Keywords: Organometallic catalysts ; Catalysis ; Reaction mechanisms ; Lithium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kinetic investigations of the polyreaction of isoprene with organolithium compounds as initiators in n-heptane as solvent indicate the following sequence of reactions: 1. formation of an adduct between a monomeric form of the organolithium compound and the isoprene and 2. reaction of this adduct with an associated form of the organolithium compound with insertion of the isoprene. The adduct formation is considered to be due to chemisorption, and proof of such chemisorption of a monomer (ethylene) is also demonstrated for a homogeneous Ziegler-type catalyst. All the reactions can be formulated in the form of cyclic structures with electron-deficient character. Postulation of such ring structures explains the surprising values obtained for the frequency factors and equilibrium constants.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196400931
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    Coordination Chemistry and Catalysis. Investigations on the Synthesis of Cyclooctatetraene by the Method of W. Reppe (1964)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 3 (1964), S. 185-191 
    Details
    ISSN: 0570-0833
    Keywords: Coordination modes ; Catalysis ; Cyclooctatetraenes ; Reppe chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The relationship between the structure and the catalytic activity of nickel(II) complexes in the synthesis of cyclooctatetraene by the method of W. Reppe is discussed. The cyclotetramerization of acetylene takes place within labile Ni(II)-acetylene π-complexes. Inhibition tests have made it probable that four molecules of acetylene are grouped around the nickel ion in the transition state, in a configuration which favors the formation of the eight-membered ring.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196401851
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    The Oxidation of Olefins with Palladium Chloride Catalysts (1962)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 1 (1962), S. 80-88 
    Details
    ISSN: 0570-0833
    Keywords: Oxidation ; Palladium ; Catalysis ; Alkenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oxidation of olefins to carbonyl compounds with palladium compounds, especially the oxidation of ethylene to acetaldehyde, is at present carried out on a technical scale. The reaction takes place via a palladium-olefin complex, the formation of which is inhibited by halide ions. Hydrolysis to the carbonyl compound is inhibited by hydrogen ions. The knowledge gained by studying the reaction of olefins with pure solutions of palladium salts allows important conclusions to be drawn concerning the action of technical catalyst solutions containing copper and palladium chloride.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/anie.196200801
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