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Absolute Configuration

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Kiyonaga Fujii – One of the best experts on this subject based on the ideXlab platform.

Kenneth Ruud – One of the best experts on this subject based on the ideXlab platform.

  • Absolute Configuration of c76 from optical rotatory dispersion
    ChemPhysChem, 2005
    Co-Authors: Prasad L Polavarapu, Jiangtao He, Jeanne Crassous, Kenneth Ruud
    Abstract:

    The Absolute Configuration of C 1 6 has been determined as (+) 5 8 9 -(C)-C 7 6 , for the first time, by comparing the experimental and predicted optical rotatory dispersion (ORD) patterns. The experimental ORD pattern was derived from the experimental electron-ic circular dichdichroism (ECD) spectrum using the Kramers-(KK) transform. The theoretical ORD spectra were calculated in the resonant region using linear response theory, and also using the KK transform of the theoretical ECD spectrum, at -different theoretical levels, namely BHLYP/6-31G*, B3LYP/6-31G*, BLYP/6-31G*, and HF/6-31G*. Good agreement noted between experimental and predicted spectra allows for an unambiguous determination of the Absolute Configuration.

Ken-ichi Harada – One of the best experts on this subject based on the ideXlab platform.

  • Determination of the Absolute Configuration of a secondary alcohol by NMR spectroscopy using difluorodinitrobenzene
    Tetrahedron Letters, 1999
    Co-Authors: Ken-ichi Harada, Youhei Shimizu, Atsuko Kawakami, Kiyonaga Fujii
    Abstract:

    Abstract A versatile method was developed to determine the Absolute Configuration of a secondary alcohol using the characteristic functions of 1,5-difluoro-2,4-dinitrobenzene (FFDNB). In this method, a secondary alcohol reacted first with FFDNB under mild basic conditions, and 1-phenylethylamine was then introduced into the secondary alcohol-FDNB derivative for the recognition by the NMR spectral method. Because the conformations of the resulting derivatives are rigidly fixed by the dinitrobenzene plane, the Absolute Configuration at the asymmetric carbon of the secondary alcohol tested can be definitively deduced using the NMR anisotropic effect.

J. Cymerman Craig – One of the best experts on this subject based on the ideXlab platform.

Gerald Bernardinelli – One of the best experts on this subject based on the ideXlab platform.

  • the use of x ray crystallography to determine Absolute Configuration
    ChemInform, 2008
    Co-Authors: H D Flack, Gerald Bernardinelli
    Abstract:

    Essential background on the determination of Absolute Configuration by way of single-crystal X-ray diffraction (XRD) is presented. The use and limitations of an internal chiral reference are described. The physical model underlying the Flack parameter is explained. Absolute structure and Absolute Configuration are defined and their similarities and differences are highlighted. The necessary conditions on the Flack parameter for satisfactory Absolute-structure determination are detailed. The symmetry and purity conditions for AbsoluteConfiguration determination are discussed. The physical basis of resonant scattering is briefly presented and the insights obtained from a complete derivation of a Bijvoet intensity ratio by way of the mean-square Friedel difference are exposed. The requirements on least-squares refinement are emphasized. The topics of right-handed axes, XRD intensity measurement, software, crystal-structure evaluation, errors in crystal structures, and compatibility of data in their relation to AbsoluteConfiguration determination are described. Characterization of the compounds and crystals by the physicochemical measurement of optical rotation, CD spectra, and enantioselective chromatography are presented. Some simple and some complex examples of AbsoluteConfiguration determination using combined XRD and CD measurements, using XRD and enantioselective chromatography, and in multiply-twinned crystals clarify the technique. The review concludes with comments on AbsoluteConfiguration determination from light-atom structures.

  • the use of x ray crystallography to determine Absolute Configuration
    Chirality, 2008
    Co-Authors: H D Flack, Gerald Bernardinelli
    Abstract:

    Essential background on the determination of Absolute Configuration by way of single-crystal X-ray diffraction (XRD) is presented. The use and limitations of an internal chiral reference are described. The physical model underlying the Flack parameter is explained. Absolute structure and Absolute Configuration are defined and their similarities and differences are highlighted. The necessary conditions on the Flack parameter for satisfactory Absolute-structure determination are detailed. The symmetry and purity conditions for AbsoluteConfiguration determination are discussed. The physical basis of resonant scattering is briefly presented and the insights obtained from a complete derivation of a Bijvoet intensity ratio by way of the mean-square Friedel difference are exposed. The requirements on least-squares refinement are emphasized. The topics of right-handed axes, XRD intensity measurement, software, crystal-structure evaluation, errors in crystal structures, and compatibility of data in their relation to AbsoluteConfiguration determination are described. Characterization of the compounds and crystals by the physicochemical measurement of optical rotation, CD spectra, and enantioselective chromatography are presented. Some simple and some complex examples of AbsoluteConfiguration determination using combined XRD and CD measurements, using XRD and enantioselective chromatography, and in multiply-twinned crystals clarify the technique. The review concludes with comments on AbsoluteConfiguration determination from light-atom structures. Chirality, 2008. © 2007 Wiley-Liss, Inc.

  • Absolute structure and Absolute Configuration
    ChemInform, 2000
    Co-Authors: H D Flack, Gerald Bernardinelli
    Abstract:

    Fundamental notions concerning Absolute structure and Absolute Configuration, and their determination from single-crystal diffraction measurements, are presented and reviewed. A glossary of terms with definitions useful in this field is provided. For Absolute structure and its determination, the separate but interacting influences of the structure and the inversion-distinguishing power of an X-ray diffraction experiment with dispersive scatterers are examined. Important experimental and algorithmic details of the current methods used for Absolute-structure determination are provided. Characterization of crystals for Absolute-structure determination and of molecules for AbsoluteConfiguration determination are treated. Attention is given to the analysis of Absolute structure and Absolute Configuration in twinned crystals.