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  • Analytical Chemistry and Spectroscopy  (2,202)
  • ASTROPHYSICS
  • Wiley-Blackwell  (2,202)
  • 1995-1999  (2,202)
Collection
Publisher
  • Wiley-Blackwell  (2,202)
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 724-728 
    ISSN: 0749-1581
    Keywords: NMR ; 11B NMR ; 13C NMR ; 1J(13C, 11B) coupling constant ; 1-alkynyldioxaborolanes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Broad 13C resonances, as the result of partially relaxed scalar 13C—11B coupling, were observed for the C-1 and to a lesser extent C-2 carbons of 1-alkynyldioxaborolanes at 25°C. Measurement of the 13C spectra at 102°C resulted in a slower 11B quadrupolar relaxation rate and allowed the determination of 1J(13C,11B) scalar coupling from the resulting quadruplets for the C-1 carbon.
    Additional Material: 1 Ill.
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  • 2
    ISSN: 0749-1581
    Keywords: NMR ; 103Rh ; 31P ; 13C ; rhodoximes ; organobis(dimethylglyoximato) rhodium ; complexes ; trans influence ; coupling constants ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 103Rh NMR chemical shifts of rhodoximes [Rh(dmgH)2(PPh3)X] (1) and organorhodoximes [Rh(dmgH)2(L)R] (2, L = PPh3; 3, L = PMe3; 4, L = P(OPh)3; 5, L = SMe2; 6, L = py) were measured with a wide range of anionic ligands X, organo groups R and axial ligands L. The chemical shifts δ(103Rh) in the halide complexes 1 show the ‘normal halogen dependence’ (Cl 〉 Br 〉 I). δ(103Rh) in 2-6 depends on the axial base L in the order py 〉 SMe2 〉 PPh3 〉 P(OPh)3 ≍ PMe3 and in 2 on the organo group R in the order Et ≍ Me 〈 nPr 〈 CH2Ph ≍ CH2OMe 〈 CH2Br 〈 CH2Cl 〈 iPr 〈 Cy 〈 CH=CH2 〈 CH2SiMe3 〈 tBu 〈 cis-CH=CHPh ≍ cis-CH=CHPr 〈 Ph ≍ C≡CPh 〈 CPr=CH2. The coupling constants 1J(103Rh,31P) in 2 reflect the (NMR) trans influence of R. There is a strong correspondence between the NMR trans influence and the structural trans influence, as indicated by the bond lengths d(Rh - P).
    Additional Material: 2 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 441-448 
    ISSN: 0749-1581
    Keywords: 125Te NMR ; 13C NMR ; 1H NMR ; diorganotellurium(II) compounds ; tetraorganotellurium(IV) compounds ; substituent effects ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 125Te, 13C and 1H NMR studies on a series of symmetric diorganotellurium(II) [R2 Te, where R = Me, Et, n-Bu, CH2SiMe3, allyl, vinyl, C≡CMe, C≡CEt, C≡C(n-Pr), C≡C(t-Bu), C≡C(SiMe3) and C≡CPh], unsymmetric diorganotellurium(II) (RTeR′) (where R = allyl, R′ = Me, Et, i-Pr, t-Bu; R = Me and R′ = benzyl), symmetric bis(alkyltelluro)ethyne (RTeC=CTeR, where R = Me and Et) and symmetric tetraorganotellurium(IV) (R4Te, where R = Me, n-Bu, CH2SiMe3 and vinyl) compounds are presented. 125Te was acquired under 1H-decoupled and 1H-coupled conditions. Whereas the 1H-decoupled 125Te NMR spectra are extremely useful in identifying low levels of tellurium containing impurities, the 1H-coupled 125Te experiments allow for structure determination and identification of long- and short-range coupling pathways. 1H and 13C NMR were used to assess purity in terms of organic materials which can include solvents, decomposition byproducts and unwanted organometallic compounds from side reactions occurring during synthesis. 125Te satellites are observed in the 1H and 13C NMR spectra and are useful in resonance assignments and in identification of long- and short-range coupling pathways. The effects of substituents on chemical shifts and coupling constants are discussed.
    Additional Material: 3 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 690-693 
    ISSN: 0749-1581
    Keywords: NMR ; 13C NMR ; 15N NMR ; 1,2,4-triazines ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C and 15N NMR spectra of eight substituted 1,2,4-triazines were measured and assigned. The assignments of the 13C NMR spectra were based on the substituent chemical shifts and nJ(C,H) coupling constants. 15N NMR chemical shifts generally showing well separated ranges were assigned by the proton coupled 15N NMR spectra. 15N NMR chemical shifts of N-4 in 3- and 5-methoxy or -thiomethyl-substituted 1,2,4-triazines were found to be related significantly (confidence level 〉99%) with the π-charge at N-4 calculated by a semi-empirical molecular orbital (AM1) procedure. For the 15N NMR chemical shifts of N-1 and N-2, no reliable correlations with the molecular electronic properties such as AM1 π-charges and ionization potentials ( - EHOMO) were found.
    Additional Material: 1 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 318-321 
    ISSN: 0749-1581
    Keywords: NMR ; 1H NMR ; 13C NMR ; INEPT ; HMBC ; nitro ; amine ; dehydroabietic acid derivatives ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reliable assignments were made for a series of nitro and amine C ring-substituted dehydroabietic acid derivatives, the main resin acid present in disproportionated rosin and an important intermediate in the chemical industry. A combination of 1D and 2D NMR techniques, including HETCORR, COSY and DEPT experiments, was used. Quaternary carbon atoms, mainly aromatic substituted, require care owing to assignment difficulties that are based on calculated data and are confirmed by long-range 1H, 13C NMR correlation with selective INEPT and the proton-detected HMBC experiment.
    Additional Material: 2 Tab.
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 367-374 
    ISSN: 0749-1581
    Keywords: NMR ; 1H NMR ; 13C NMR ; antidepressants ; trimipramine maleate ; nitrogen inversion ; molecular dynamics ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solution conformations and dynamics of the antidepressant drug trimipramine maleate were investigated by 1H and 13C NMR spectroscopy. Of particular interest was an observed non-equivalence of the N-methyl groups in the aliphatic side-chain of the drug, which is present in both 1H and 13C spectra under a range of aqueous and non-aqueous solvent conditions when the terminal nitrogen is protonated. Although the inequivalence was first observed for the maleate salt, the nature of the counter ion is not a determining factor. The solution concentration of the drug does, however, modulate the observed inequivalence, with the two peaks coalescing at higher drug concentrations. The diastereotopic environments of the two methyl groups arise because of a chiral centre in the aliphatic side-chain. Inversion of the terminal nitrogen produces exchange between the two environments, thereby destroying the inequivalence and leading to a single averaged resonance for the two methyl groups. The energy barrier for the exchange process was determined from variable-temperature NMR experiments to be 16.3 kcal ml-1 (1 kcal = 4.184 kJ). This is higher than would be expected for simple inversion of a tertiary nitrogen, but reflects the fact that inversion can only occur for the small fraction of molecules which are not protonated. The barrier determined from the variable-temperature experiments was in agreement with rates of interchange between the two methyl environments determined from saturation transfer experiments. These rates were measured for a series of different protonation states of the nitrogen, with the rate contant for interchange of environments decreasing with an increasing degree of nitrogen protonation. 13C spin-lattice relaxation times and nuclear Overhauser enhancement effects were also measured to determine the degree of mobility in the aliphatic side-chain of trimipramine maleate.
    Additional Material: 7 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 497-499 
    ISSN: 0749-1581
    Keywords: NMR ; 1H NMR ; 13C NMR ; 6-s-trans-retinoids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new class of vitamin A analogs (retinoids) was synthesized containing a dimethylene bridge to maintain a 6-s-trans conformation of the terminal double bonds. The 1H and 13C NMR spectra were assigned for 15 new compounds, including E-Z isomers (all-E, 13Z, 9Z and 9Z,13Z) of retinoids containing an ethyl ester and car-boxylic acid polar end groups, and also the (all-E)-isomer of the retinoids with an alcohol and aldehyde polar end-groups and five C15 intermediates. The assignments were based on long-range 1H—13C heteronuclear 2D experiments.
    Additional Material: 1 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 917-921 
    ISSN: 0749-1581
    Keywords: NMR ; 13C-NMR ; alk-2-yn-1-ols ; ω-alkyn-1-ols ; internal alkyn-1-ols ; chemical shifts ; OH shift increments ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C NMR chemical shifts of three types of unbranched alkyn-1-ols were measured and assigned: alk-2-yn-1-ols, ω-alkyn-1-ols and ‘internal’ alkyn-1-ols. The derived OH shift increments depend on the number of CH2 groups between the triple bond and the OH group.
    Additional Material: 5 Tab.
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  • 9
    ISSN: 0749-1581
    Keywords: NMR ; 13C NMR ; chemical shift ; sulphonated compounds ; fluorosulphonic acids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A chemical shift analysis of the 13C NMR spectra of more than 50 acyclic sulphonic acids, alkali metal sulphonates and methyl esters was carried out. Chemical shift increment systems with n-alkanes as reference molecules were established for linear alkanesulphonates and alk-2-enesulphonates. Some short-chain fluorinated sulphonic acids were also studied, especially pentafluorothio derivatives. C—F spin-spin coupling constants were determined. Pauling electronegativity values for SO3H and SF5 groups were derived from α chemical shift increments.
    Additional Material: 5 Tab.
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 27-33 
    ISSN: 0749-1581
    Keywords: 13C NMR ; 31P-13C coupling constants ; 13C-1H coupling constants ; Dialkyl α-anilinobenzylphosphonates ; Dialkyl α-anilino-(2-hydroxybenzyl)phosphonates ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C NMR spectra of a series of dialkyl α-anilinobenzylphosphonates and dialkyl α-anilino-(2-hydroxybenzyl)phosphonates were measured. The assignment of the spectra was performed using a combination of 31P-13C and 13C-1H coupling constants and substituent-induced chemical shifts. Long-range phosphorus-carbon couplings up to five bonds were observed.
    Additional Material: 2 Ill.
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