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  • Electronic Resource  (7)
  • Chemistry  (7)
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  • 1
    Electronic Resource
    Electronic Resource
    Photochemische Reaktionen. 53. Mitteilung [1]. Photochemische Addition von Alkylaromaten an Aryl-Carbonylverbindungen (1969)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 52 (1969), S. 1010-1015 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the preceding paper [1] a novel primary photochemical process of triplet excited α,β-conjugated cycloalkenones in toluene solution has been reported: the abstraction of a benzylic hydrogen from the solvent by the β-carbon (cf. 1 → 2 + 3 + 4). The reaction has been attributed to the π,π* triplet.Aromatic aldehydes and ketones (5-11a), the triplet state reactivity of which is known to be mostly π,π* in nature, have now been examined under the same irradiation conditions. However, a reaction similar to that of cycloalkenones  -  expected to result in the addition of hydrogen to the ortho and para positions of the aryl moiety and the formation of benzylcyclohexa-1,3-and 1,4-diene derivatives  -  could not been found. Compounds 5-10 remained essentially unchanged. 4-Methoxyacetophenone (11a) reacted slowly to form the same type of products [tert-carbinol 12a, pinacol 13a and dibenzyl (4)] as the aromatic carbonyl compounds 11b-d, benzophenone and cyclopropylphenylketone, which exhibit typical n,π* triplet reactivity (hydrogen abstraction by the carbonyl oxygen).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19690520415
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  • 2
    Electronic Resource
    Electronic Resource
    Photochemische Reaktionen. 52. Mitteilung [1]. Zur Photochemie von α,β-ungesättigten cyclischen Ketonen: Spezifische Reaktionen der n,π*- und π,π*-Triplettzustände von O-Acetyl-testosteron und 10-Methyl-Δ1,9-octalon-(2) (1969)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 52 (1969), S. 971-1009 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photochemistry of the conjugated cyclohexenones O-acetyl testosterone (1) and 10-methyl-Δ1,9-octalone-(2) (24) has been investigated in detail. The choice of reaction paths of both ketones depends strongly on the solvent used. In t-butanol, a photostationary equilibrium 1 ⇄ 3 is reached which is depleted solely by the parallel rearrangement 1 → 5 (Chart 1; for earlier results on these reactions see [2a] [6] [7]). In benzene, double bond shift 1 → 16 (Chart 3) occurs instead, which is due to hydrogen abstraction from a ground-state ketone by the oxygen of an excited ketone as the primary photochemical process. In toluene, the major reaction is solvent incorporation (1 → 17, Chart 4) through hydrogen addition to the β-carbon of the enone, accompanied by double bond shift and formation of saturated dihydroketone as the minor reactions. Contrary in part to an earlier report [19], the photochemical transformation of the bicyclic enoné 24 exhibit a similar solvent dependence. The corresponding products 25-29 are summarized in Chart 5 and Table 1.Sensitization and quenching experiments established the triplet nature of the above reactions of 1 and 24. Based on STERN-VOLMER analyses of the quenching data (cf. Figures 2, 4-8, and Table 3), rearrangement, double bond reduction and toluene addition are attributed to one triplet state of the enones which is assigned tentatively as 3(π, π*) state, and the double bond shift is attributed to another triplet assigned as 3(n, π*) state (cf. Figure 9).The stereospecific rearrangement of the 1α-deuterated ketone 2 to the 4β-deuterio isomer 4 shows the reaction to proceed with retention at C-1 and inversion at C-10.The 4-substituted testosterone derivatives 33-36 (Chart 8) were found to be much less reactive in general than 1. In particular, 4-methyl ketone 33 remains essentially unchanged on irradiation in t-butanol, benzene and toluene.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19690520414
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  • 3
    Electronic Resource
    Electronic Resource
    Photochemische Reaktionen. 43. Mitteilung [1]. UV.-Bestrahlung von N-Phenylurethan und N-Phenylthiourethan (1968)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 51 (1968), S. 221-224 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ultraviolet irradiation of N-phenylurethane (I) solutions with wavelength 253,7 nm resulted in the formation o polymeric material, the characteristic pattern of monomeric products associated with Photo-FRIES-type rearrangements [→ ethyl anthranilate (II), ethyl p-aminobenzoate (III)], and accompanying dissociation products [→ aniline (IV)].N-Phenylthiourethance (V) showed no tendency to undergo Photo-FRIES-type rearrangements. Formation of polymeric material and aniline (IV), and in the presence of molecular oxygen, cyclodehydrogenation to the 2-ethoxy-benzthiazol (VI) as well as a ready exchange of the sulfure atom in V by oxygen occurred instead.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19680510127
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  • 4
    Electronic Resource
    Electronic Resource
    Photochemical Reactions. Part 64 [1]. The photochemistry of 3-alkyl-cyclopent-2-en-ones (1971)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 54 (1971), S. 1517-1531 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On ultraviolet irradiation in toluene, cyclopent-2-en-one (1a) and 3-methylcyclopent-2-en-one (1b) undergo dimerisation (→ 3a, b, 4b), whereas 3-t-butyl-cyclopent-2-en-one (1e) and the bicyclo [3.2.1]octenone 2a only react with the solvent (→ 5e-7e, 8-10). The 3-ethyl-(1c) and 3-isopropyl-cyclopent-2-en-ones (1d) afford by dimerisation products 3c, d, 4c and by reaction with the solvent 5c, d, 6c, d, 7d. The β-methoxy-enones 1f and 2b are unreactive under comparable irradiation conditions. The head-to-head cyclobutane dimer 3b (HH) by separate irradiation at 〈 3400 Å in toluene, is reconverted to 1b. By similar irradiation each of the head-to-tail dimers 3b (anti- and syn-HT) and also the unsaturated dimer 4b give a new isomer of unknown structure besides small amounts of monomer 1b and relatively large amounts of insoluble material.The photoreactions of 1b-e can be quenched by naphthalene. Stern-Volmer plots for the quenching of the dimers of 1b, 1c, and 1d, and of 3-t-butylcyclopentanone (5e) and the dihydro dimer 7e are linear and within each experiment, the slopes satisfactorily coincide, whereas the slope for the α-benzyl ketone 6c is distinctly greater than that for the dimers 3c. A similar differentiation, although less pronounced, is found between the benzyl ketones 6d and 6e and the respective accompanying products.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19710540602
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  • 5
    Electronic Resource
    Electronic Resource
    Thermische, nichtkatalysierte Cycloadditionen der Acrylverbindungen an Cycloheptatrien (1971)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 54 (1971), S. 463-473 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cycloaddition reactions of cycloheptatriene with acrylonitrile and methyl acrylate have been investigated in some detail. The exo (1) and endo (2) adducts resulting from the [2+2+2]-cycloaddition of acrylic components to the 2,5-positions of cycloheptatriene have been separated and the structures have been elucidated by NMR. The by-products are 7-endo-substitued derivatives of bicyclo[4,2,1]nona-2,4-diene (3), resulting from the formal [6+2]-cycloaddition to the 1,6-positions of cycloheptatriene. The mechanism of their formation is discussed.Irradiation (λ = 253,7 nm) of 3 in various solvents gave an almost quantitativ yield of [2+2]-cyclodimers of the 14 type. No intramolecular photocyclization of 3 to cyclobutenes 13a and/or 13b was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19710540205
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  • 6
    Electronic Resource
    Electronic Resource
    Lösungsmittel-sensibilisierte strahlungschemische Reaktionen II FRIES-Umlagerungen von Arylestern und Arylamiden [1] (1968)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 51 (1968), S. 1980-1989 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a series of screening experiments p-tolyl acetate (1a), phenyl benzoate (1b), p-tolyl benzoate (1c), acetanilide (1d), and 2-naphthyl acetate (5) have been subjected to γ-radiolysis in aromatic and saturated hydrocarbon solutions. Qualitatively, the products formed correspond to those observed also with the respective photo-FRIES reactions, i.e., hydroxy- and amino-aryl ketones due to rearrangements, and products due to homolytic fission into aryloxy and aniline radicals, respectively, were produced.The relatively high G values of conversion in dilute solutions indicate that energy transfer from the solvent is operative. E.g., 0,1 M p-tolyl acetate (1a) in benzene has a G value of over 0.3 for ortho-rearrangement to 2a, and of 0.55 for cresol (4a) formation. Kinetic evidence points to different energy requirements of the ortho-rearrangement and the phenol formation, and to more than one excited state of benzene acting as energy donor. The ratio of the observed rate constants of the energy transfer to self-quenching in benzene is about 80 1 · mole-1 for the ortho-rearrangement to 2a. The over-all reaction is strongly quenched upon addition of p-terphenyl.A comparison of the quantitative data obtained in this work with available published data reveals differences between benzene-sensitized runs with γ radiation and photochemical experiments. Thus, the ratios of ortho vs. para and amphi rearrangement, and of homolytic fission vs. rearrangements are higher in the solvent-sensitized radiolyses.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19680510817
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  • 7
    Electronic Resource
    Electronic Resource
    Photoinitiated rearrangements in poly[2,2-propanebis(4-phenyl carbonate)] (1966)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Letters 4 (1966), S. 1-5 
    Details
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1966.110040101
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