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  • Organic Chemistry  (31)
  • Inorganic Chemistry  (28)
  • Wiley-Blackwell  (59)
  • Institute of Physics
  • International Union of Crystallography
  • 1985-1989
  • 1980-1984  (59)
  • 1970-1974
  • 1940-1944
  • 1984  (59)
Collection
Publisher
  • Wiley-Blackwell  (59)
  • Institute of Physics
  • International Union of Crystallography
Years
  • 1985-1989
  • 1980-1984  (59)
  • 1970-1974
  • 1940-1944
Year
  • 1
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pure pencillin N α-sulfoxide (1) and penicillin N β-sulfoxide (2) were obtained by HPLC and tested as substrates for deacetoxycephalosporin C synthetase (DXCS). Neither one of the sulfoxides was utilized under conditions of conversion of penicillin N (8) to deacetoxycephalosporin C (9). The cephalosporin C α and β-sulfoxides (3 and 4, resp.) were also prepared. Relative stabilities of the sulfoxides 3 and 4 are discussed by interpretation of the 13C-NMR spectra.
    Additional Material: 9 Ill.
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  • 2
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the crystal structure of the title compound at 98 K the dimethylamino group has pyramidal geometry. The nitrogenlone pair is not directed towards the triple bond; instead, one N—CH3 bond lies almost in the plane of the disubstituted ring, directed away from the triple bond, while the other N—CH3 bond and the lone pair are directed to opposite sides of the plane, nearer to the acetylene. There is a remarkably short intramolecular contact (2.39 Å) between a methyl H- and an acetylenic C-atom. The Taft σI parameter of the arylethynyl substituent appears to be similar to that of a carboxylic ester, judging from the bond-angle deformation at the ipso-C-atom.
    Additional Material: 5 Ill.
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  • 3
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of 2-dimethylaminobenzenediazonium tetrafluoroborate has been determined at 183 K by X-ray diffraction. The cation is very nearly planar, the strong steric interaction between the ortho-groups being diminished by in-plane angular distoritions.
    Additional Material: 3 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 512 (1984), S. 211-220 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Darstellung und physikochemische Untersuchung der Nickel (II)-Komplexe mit Salizylaldehyd-S-methylthiosemicarbazonSalizylaldehyd-S-methylthiosemicarbazon (H2L) bildet mit NiII in Gegenwart von NO3- und ClO4- paramagenetische bis-Ligand-Chelat-Komplexe und in Gegenwart von NCS-, CH3COO-, Py und γ-Picolin diamagnetische, quadratisch-planare mono-Ligand-Chelat-Komplexe. In den paramagnetischen Komplexen wird H2L als neutrale Molekel und auch als Monoanion (HL-) koordiniert, in diamagnetischen Komplexen ausschließlich als Monoanion, mit Ausnahme des Komplexes in Gegenwart von CH3COO-, wo sich Salizylaldehyd-S-methylthiose micarbazon als Dianion (L2-) koordiniert. Letztere Liganden entstehen infolge der Deprotonierung der NH2- neben der OH-Gruppe. Die Komplexe wurden durch Elementaranalyse, magnetische Messungen, IR, Elektronenspektren, molare Leitfähigkeit und TG-Analysen charakterisiert.
    Notes: Salicylaldehyde S-methylthiosemicarbazone (H2L) in the presence of ClO4- forms with NiII the paramagnetic octahedral bis(ligand) chelate complexes while in the presence of NCS-, CH3COO-, Py and γ-Pic it gives diamagnetic square planar mono(ligand) chelate complexes. In the paramagnetic complexes H2L is coordinated as a neutral molecule (H2L) and monoanion (HL-), and in diamagnetic ones only as a monoanion, except the complex obtained in the presence of CH3COO-, where it is coordinated as a dianion (L2-). The last form of the ligand is the result of deprotonation, besides OH-, the NH2-group. The complexes have been characterized by elemental analysis, magnetic measurements, i.r. and diffuse-reflection spectra, molar conductivity and TG analysis.
    Additional Material: 5 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 67 (1984), S. 2155-2160 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hyperbolic reaction curves with concentration-independent relaxation times are obtained from the simple reaction scheme A⇌I + P; A + I → P. While a mathematically perfect hyperbola is only obtained, if two of the three rate constants are accidentally degenerate, the same function can still be used as a very close approximation in the general case, and the differences may go unnoticed even for well-defined stopped-flow experiments. In view of the simplicity of the reaction, it is suggested that reaction curves with second-order (hyperbolic) shapes, but concentration-independent relaxation times may be a common feature in chemical kinetics.
    Additional Material: 3 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 67 (1984), S. 1019-1025 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The catalytic activity of autoxidized copper (I) in the oxidation of para-disubstituted benzoins in dimethylsulfoxide by O2 was studied both kinetically and by product analysis. Stoichiometry (1), accounts for more than 80% of the reaction. The catlytic oxydation was followed by monitering th consumption of O2 manometrically by a fully automatic apparatus. (X = H, CH3, OCH3, C6H5 CI)A redox shuttle mechanism is proposed, where the rate-determining step is the autoxidation of Cu(I) followed by a rapid oxidation of the substrate by an oxocupric species. The redox stiochiometry (I) corresponds to that found for external monooxy-genases (or mixed-function oxidases), and the significance of our results with respect to analogous catalytic systems is discussed.
    Additional Material: 3 Ill.
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  • 7
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complexation of Cu(I) and Cu(II) by a series of 12-, 14- and 16-membered macrocyclic ligands 1-6 containing the N2S2 donor set has been studied potentiometrically, spectrophotometrically and voltammetrically.In the case of Cu(II), mononuclear complexes CuL2+ with stability constants of 1010-1015 are formed. In addition, partially hydrolyzed species Cu(L)OH+ are observed at pH 〉 10 for the 12-membered ligands. For Cu(I), beside the specis CuL+ with stabilities of 1012-1014, the unexpected formation of protonated species CuLH2+ was detected. In contrast to the well-known general trends in coordination chemistry, the stability of these protonated species increases relative to that of the complexes with the neutral ligand when the ring size and concomitantly the distance between neighbouring donor atoms is decreased. From the stability constants of the Cu(I)- and Cu(II)-complexes the redox potentials have been calculated and are compared to the values of E1/2 obtained by cyclic voltammetry. Despite the identical donor set the Cu(II)/Cu(I) redox potentials of the complexes are spanning a range of 340 mV or six orders of magnitude in relative stability, reflecting the importance of subtle differences in steric requirements.
    Additional Material: 2 Ill.
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  • 8
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The autoxidation of the Cu+ complexes with a series of six 12-, 14- and 16-membered macrocycles containing the N2S2 set of donor atoms has been studied with an oxygen electrode and with the stopped-flow technique. Inspite of the identical set of coordinating groups, the reactivity of the Cu= complexes towards O2 varies by more than 5 orders of magnitude, with rate constants between 〈0.1 and 2·104 M-1S-1. Simple bimolecular rate laws are obtained from initial rates of autoxidation, but successive one-electron transfers with intermediate formation of superoxide are implied from the analysis of complete reaction curves for complexes with the 12-membered macrocycles. The kinetic parameters are compared with the redox potentials for the corresponding CuL2+/CuL+ couples. Only a rather rough correlation is found and steric factors must in addition be responsible for the observed reactivity pattern which shows a decrease of autoxidation rate with increasing size of the macrocyclic ring. No systematic effect was observed for the influence of cis- vs. trans-configuration of the donor atoms.
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 67 (1984), S. 612-615 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new short route to chenodeoxycholic acid has been developed. The synthesis is based on the stereoselective introduction of the steroidal side chain via an ene reaction of methyl acrylate and a (17Z)-ethylidene steroid prepared from androstenedione.
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  • 10
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Phenylthiomethyllithium/N,N,N′,N′-tetramethylethylenediamine (TMEDA) (1:1) is shown by X-ray analysis to be dimeric in the crystalline state. The structural unit contains a six-membered ring in which each Li is bonded to the terminal C atom of one thioanisole and to the S atom of the other, as well as to the two N atoms of a TMEDA. Methylthiomethyllithium/TMEDA (1:1) is also dimeric, but the structural unit contains a four-membered ring in which each Li is bonded to two C atoms and to the two TMEDA N atoms. An error has been detected in an earlier published electron-density difference map for 2-lithio-2-phenyl-1, 3-dithiane/TMEDA/THF (1:1:1). The conclusion drawn then that this complex exists as a tight ion-pair in the crystal is now retracted.
    Additional Material: 6 Ill.
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