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  • 1
    Electronic Resource
    Electronic Resource
    Mathematical model for the optimization of the reaction between 2,3-bis(m-tolyl)quinolizinium bromide and piperidine using a factorial design (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 1-10 
    Details
    ISSN: 0886-9383
    Keywords: Derivatization reaction ; Factorial design ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A number of nucleophiles have been successfully identified and quantified using the Kröhnke reaction with 2,3-diphenyl derivatives of quinolizinium salts. Optimization of the reaction conditions by means of a mathematical model involving analysis of the response surface has led to a better understanding of the factors exerting an influence on the above reaction.The parameters chosen were temperature, reaction time, base concentration, water concentration and nucleophile concentration. The reaction was developed in polar aprotic solvents (acetone, acetonitrile). To facilitate the nucleophilic attack, the presence of an organic base (triethylamine) was necessary, although concentrations in excess of 0·15M did not alter the development of the reaction. Since pharmaceutical solutions are often aqueous, the influence of water on the reaction was studied. Low water volumes have no significant influence on the opening of the quinolizinium ring by the nucleophilic reagent. However, when the water proportion exceeded that of the organic solvent, the fluorescence intensity was lower than expected. Development of the fluorescent reaction product was first detected 5 min after the reaction started. The fluorescence intensity reached its optimum value after 138 min.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060102
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  • 2
    Electronic Resource
    Electronic Resource
    A simplified method for deuterium/hydrogen isotope ratio measurements on water samples of biological origin (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 22 (1993), S. 383-387 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Equilibration of hydrogen gas with the water in a variety of biological sample materials was carried out in Vacutainers using platinum-on-alumina catalyst physically isolated from the liquid water. The equilibration takes 3 days at room temperature - much slower than with catalysts which float on the water surface - but this reduces the short-term temperature sensitivity of the procedure, and the inexpensive materials used allow convenient disposal of biologically contaminated samples after analysis. The slow equilibration also allows time for complete exchange with water contained in a complex sample matrix such as plant stems or soil without the need for prior isolation of the water sample. The method has particular application in studies of human total body water where repeated studies can be carried out over a short time period without the need to wait for the previous dose to wash out. Water turnover rates from total diurnal energy expenditure studies measured by this method were not significantly different from those obtained by the zinc reduction method.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200220704
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  • 3
    Electronic Resource
    Electronic Resource
    Urinary metabolites of L-threonine in type 1 diabetes determined by combined gas chromatography/chemical ionization mass spectrometry (1986)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 13 (1986), S. 535-540 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metabolic profiling of urinary organic acids from patients with juvenile-onset (Type 1) diabetes mellitus have revealed significantly elevated levels of 2-hydroxybutyric acids. To test the hypothesis that these metabolites, as well as 4-deoxyerythronic acid, are derived from L-threonine, stable isotope-labeled threonine was infused into an insulin-deficient dog and the incorporation of 13C into these metabolites was monitored by gas chromatography/mass spectrometry. Electron ionization was relatively insensitive, but positive chemical ionization with ammonia as the reactant gas gave both protonated molecules and [M+NH4]+ ions, which could be analysed by selected ion monitoring. The isotope-labeled species of 2-hydroxybutyric, 4-deoxyerythronic and 4-deoxythreonic acids were observed, but 13C was not incorporated into other organic acids. Thus, it is proposed that L-threonine is a precursor of these metabolites.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200131004
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  • 4
    Electronic Resource
    Electronic Resource
    Constantes de couplage de vinylallènes (1975)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 7 (1975), S. 315-319 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: In order to define the influence of an allenic type conjugation, the NMR spectra of vinylallene and of some of its methyl derivatives are analysed The signs of the coupling constants are also determined. These compounds are characterised by a planar s-trans structure of the two noncumulated double bonds. A discussion of the parameters, and especially of the methyl replacement effects, evidences the importance of the π type contributions. The theoretical calculations of the coupling constants by the methods of finite perturbation CNDO and INDO corroborate this interpretation.
    Notes: Afin de préciser l'influence d'une conjugaison de type allénique les spectres RMN du vinylallène et de plusieurs de ses dérivés méthylés ont été analysés et les signes des constantes de couplage ont été déterminés. Ces composés présentent une structure s-trans plane des deux doubles liaisons non cumulées. Une discussion des paramètres et no amment de l'influence des substitutions méthylées fait ressortir une forte prédominance des contributions de type π. Cette interprétation est corroborée par les calculs théoriques des constantes de couplages, effectués par la méthode de perturbations finies CNDO et INDO.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270070705
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  • 5
    Electronic Resource
    Electronic Resource
    Etudes configurationnelles et conformationnelles de quelques chlorures de désoxy-6 β-L-héxopyrannosyle chlorosulfonyles et de leurs glycosides de méthyle (1975)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 7 (1975), S. 366-371 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: A total analysis of the NMR spectra of 6-deoxy-L-hexopyranoses in the α-configuration and of the corresponding β-anomers was carried out. The parameters obtained are characteristic of a 1C (L) chair conformation, having the anomeric substituent in an axial orientation for the methyl α-fuco-, α-rhamno- and α-chinovopyranosides and for the α-fuco- and α-rhamnopyranosyl chlorides. The structure is also of a 1C (L) chair type for the methyl β-fuco- and β-chinovopyranosides; the geometry is the same for the β-fuco- and β-rhamnopyranosyl chlorides despite the anomeric effect of a chlorine atom. However, the NMR parameters of the β-chinovopyranosyl chloride are not explicable on the basis of a chair conformation with an equatorial chlorine or a boat structure.
    Notes: Une analyse complète des spectres RMN de désoxy-6 L-hexopyrannoses de configuration α et des anomères β correspondants est réalisée. L'ensemble des paramètres obtenus confirme l'existence d'une structure chaise 1C (L) présentant une disposition axiale du substituant anomère dans le cas des α-fuco-, α-rhamno- et α-chinovopyrannosides de méthyle et des chlorures de α-fuco- et α-rhamnopyrannosyle. La structure reste de type chaise 1C (L) dans le cas des β-fuco- et β-chinovopyrannosides de méthyle. Il en est de même en dépit de I'effect anomère dû à I'atome de chlore, pour les chlorures de β-fuco-et β-rhamnopyrannosyle. Par contre les paramètres RMN du chlorure de β-chinovopyrannosyle ne semblent interprétables ni sur la base d'une géométrie chaise à chlore équatorial ni par une structure bateau.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270070803
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  • 6
    Electronic Resource
    Electronic Resource
    Application of 15N spectroscopy and dynamic NMR to the study of ureas, thioureas and their lewis acid adducts (1980)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 13 (1980), S. 396-402 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rotational barriers and 15N chemical shifts have been measured in a number of ureas and thioureas. As anticipated on the basis of the 15N shifts, several previously unobserved rotational barriers could be detected by using lanthanide reagents or a high field spectrometer. Nearly constant effects on both the rotational activation energy and the 15N shift are produced on going from ureas to the corresponding thioureas, and correlations are found between the ΔG
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270130603
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  • 7
    Electronic Resource
    Electronic Resource
    Constantes de Couplage en Serie Pyridinique. Application de la Theorie des Orbitales Moleculaires (1971)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 3 (1971), S. 661-677 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Coupling constants of 35 substituted pyridines are discussed and related to the electronic properties of the substituents and to the mechanism of coupling. A calculation of J is performed using Pople and Santry's theory and mutual polarizabilities obtained by CNDO/2 or Hoffmann methods. The influence of bicentric integrals on the theoretical values of J is examined.
    Notes: Les constantes de couplages relatives à un ensemble de 35 pyridines substituées sont discutées en relation avec les propriétés électroniques des substituants et le mécanisme du couplage. Un calcul de J est réalisé, sur la base de la théorie de Pople, à l′aide des valeurs de polarisabilités mutuelles obtenues par la méthode CNDO/2 et la méthode d'Hoffmann. L'influence d′une inclusion des intégrales bicentriques est examinée.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270030605
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  • 8
    Electronic Resource
    Electronic Resource
    Recherches sur la stéréochimie des diènes fonctionnnels - XI: Interprétation théorique des déplacements chimiques de stéréoisomères D'éthoxybutadiènes-1,3 (1973)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 5 (1973), S. 271-274 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: A theoretical analysis of the proton chemical shifts of alkoxy-1,3-diene stereoisomers is proposed. The diamagnetic contribution is calculated from π and σ theoretical indices obtained by the CNDO/2 method. This effect depends on the stereochemistry of the molecule and the charges and chemical shifts alternate in the same way. The diamagnetic part is often small compared to the experimental value, however, and the paramagnetic contribution Δδp is important. Δδp is difficult to explain with the usual models of anisotropic and electric contributions, but the results give useful information on the conformations of the molecules.
    Notes: Une analyse théorique des déplacements chimiques protoniques de stéréoisoméres alcoxydiéniques est proposée. La contribution diamagnétique est évaluée à partir des indices théoriques π et σ obtenus par un calcul de type CNDO/2; ce terme qui dépend de la stéréochimie ne suffit pas à expliquer les écarts expérimentaux, bien que l'alternance des charges refléte celle des déplacements chimiques; la contribution paramagnétique est importante mais reste mal expliquée dans le cadre des méthodes approchées de calcul des effects d'anisotropie et de champélectrique. Cependant l'analyse des résultats apporte des informations sur la nature des équilibres conformationnels au niveau de la liaison=C—O—.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270050605
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  • 9
    Electronic Resource
    Electronic Resource
    Etudes des sélénophènes mono et bisubstitués par Résonance Magnétique de 1H et de 13C (1974)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 6 (1974), S. 648-653 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Proton and carbon magnetic resonance spectra of mono-and disubstituted selenophenes are investigated. The proton chemical shifts are discussed in terms of magnetic anisotropy and electric field effects of the substituents, with a view to studying the conformational equilibrium of the carbonyl group. π Electronic charges, computed by the PPP method, are correlated with the proton and carbon chemical shifts. The coupling constants between 13C and 1H (1, 2 or 3 bonds) and 13C—77Se are shown to be good structural parameters and a set of substituent additivity constants is calculated.
    Notes: Une série de sélénophènes mono- et bisubstitués est étudiée en résonance de 1H et 13C. Les déplacements chimiques protoniques sont analysés en termes d'effets d'anisotropie et de champ électrique des substituants et utilisés à une discussion des équilibres conformationnels. Les relations entre δ1H et δ13C et les charges π calculées par la méthode PPP sont examinées. Les couplages 1J(13C—H), nJ(13C ∼ H) et 1J(13C—77Se) se révèlent de bonnes caractéristiques structurales et des relations d'additivité sont dégagées pour δ13C.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270061209
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  • 10
    Electronic Resource
    Electronic Resource
    Theoretical and empirical calculations of the carbon chemical shift in terms of the electronic distribution in molecules (1975)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 7 (1975), S. 2-17 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The principles of the theoretical calculations of the carbon atom screening constant are reviewed. The Independent Electron, SCF—MO and Valence Bond formulae are briefly discussed, and the relative importance of the different terms involved in an approximate decomposition of σ13C are pointed out. The variations of the excitation energy ΔE, the mean distance between the nucleus and 2p electrons, and the electronic charges and bond orders with the structure are presented. The nature of the steric effect is also explained. In a second part the various empirical correlations which make an evaluation of δ13C from structural and physical properties possible are shown. The actual substituent parameters of the main classes of compounds are listed and worked examples given to make the use of the tables easier. The correlations between δ13C and the electronic charge, electronegativity, Hammett-Taft constants, electric field effects, geometrical parameters, spectroscopic data (electronic transitions, screening of other nuclei) and pH are also discussed with a view to appraising the carbon screening.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270070103
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