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  • 1
    Electronic Resource
    Electronic Resource
    Gas chromatographic enantiomer separation of agrochemicals and polychlorinated biphenyls (PCBs) using modified cyclodextrins (1994)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 859-864 
    Details
    ISSN: 0935-6304
    Keywords: Enantioselective gas chromatography ; Cyclodextrin derivatives ; Polychlorinated pesticides ; Polychlorinated biphenyls (PCBs) ; Pyrethroid insecticides/Allethrin ; Organophosphorus pesticides/Acephate, Malaoxon ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantiomers of the polychlorinated polycyclic xenobiotics heptachlor, cis- and trans-chlordane, cis- and trans-heptachlorepoxide, oxychlordane, and bromocyclen have been resolved by gas chromatography with selectively substituted cyclodextrins. The order of elution of these compounds and of α-hexachlorocyclohexane (α-HCH) was determined by comparison with enantiomerically enriched reference compounds obtained by preparative enantioselective gas chromatography.A separation of the eight stereoisomers of the pyrethroid insecticide allethrin into seven peaks was achieved. Both trans-diastereomers were separated into their enantiomers and the order of elution could be determined by comparison with commercially available (S)-bioallethrin and trans-bioallethrin. Also one cis-diastereomer was separated, wheras the other cis-isomer could not be resolved. In addition 15 out of 19 stable atropisomeric polychlorinated biphenyls with 5, 6 and 7 chlorine substituents, some chiral organophosphorus pesticides, including acephate and malaoxon and the herbicide bromoacil were separated.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240171209
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  • 2
    Electronic Resource
    Electronic Resource
    Gas chromatographic enantiomer separation of agrochemicals using modified cyclodextrins (1991)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 14 (1991), S. 530-536 
    Details
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Heptakis(2-O-methyl-3,6-di-O-pentyl)-γ-cyclodextrin ; Mixed cyclodextrin derivatives ; Phenoxypropionic acid herbicides ; Polychlorinated pesticides ; Enantiomer separation of chlordane ; Organophosphorus pesticides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantiomers of phenoxypropionic acid type herbicides have been resolved by capillary gas chromatography employing modified cyclodextrins as chiral stationary phases. Excellent separations were obtained with columns containing a 1:1 mixture of per-O-pentylated and per-O-methylated γ-cyclodextrin.The enantiomers of the methyl esters of mecoprop and dichlorprop were also resolved on octakis(3-O-butyryl-2,6-di-O-pentyl)-γ-cyclodextrin. On this phase the order of elution of the enantiomers was temperature-dependent, the elution order being reversed as the temperature passed through the isoenantioselective temperature. This is the first time such behavior has been observed with cyclodextrin derivatives.The enantiomers of the polychlorinated polycyclic pesticides cis- and trans-chlordane, oxychlordane, heptachlor, heptachlorepoxide, and three chiral organophosphorus pesticides could be resolved using selectively derivatized cyclodextrin derivatives.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240140804
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  • 3
    Electronic Resource
    Electronic Resource
    Gas chromatographic separation of atropisomeric alkylated and polychlorinated biphenyls using modified cyclodextrins (1993)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 376-378 
    Details
    ISSN: 0935-6304
    Keywords: Resolution of atropisomers ; Alkylated biphenyls ; Polychlorinated biphenyls (PCBs) ; Dynamic gas chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Selectively alkylated cyclodextrins have been used to resolve the enantiomers of 2,2′ alkylated biphenyls. The configurational stability of 2,2′-dimethyl and 2,2′-diethyl biphenyls is insufficient for gas chromatographic separation even at ambient temperature. 2-Isopropyl-2′-t-butyl- and 2,2′-di-t-butylbiphenyl are configurationally stable under the conditions applied, whereas 2,2′-diisopropyl- and 2,2′-bis(trifluoromethyl)biphenyl show temperature-dependent interconversion of the enantiomers during chromatography. The gas chromatographic separation of the enantiomers of some ortho trichlorinated biphenyls carrying 4, 5, and 6 chlorine substituents has been demonstrated for the first time.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240160609
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of substituents on the rotational energy barrier of atropisomeric biphenyls  -  studies by polarimetry and dynamic gas chromatography (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 781-786 
    Details
    ISSN: 0947-3440
    Keywords: Atropisomers ; Biphenyls, axially chiral ; Enantiomerization ; Dynamic gas chromatography ; Polarimetry ; Energy barriers ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have synthesized a series of 2,2′-substituted biphenyls and particularly derivatives of 2,2′-bis(trifluoromethyl)biphenyl (4) with either one or two fluoro, chloro, bromo, amino, nitro or methoxy substituents in the para positions for investigating the influence of these substituents on the rotational energy barrier of the biphenyls by polarimetry and dynamic gas chromatography (DGC). Axially chiral biphenyls with at least two bulky substituents in the ortho positions were separated by gas chromatography on selectively modified cyclodextrins. Due to competition between resolution and enantiomerization in the gas chromatographic column 2-tert-butyl-2′-isopropyl- (2), 2-isopropyl-2′-(trifluoromethyl)biphenyl (5), and some para-substituted derivatives of 4 show temperature-dependent interconversion profiles and coalescence phenomena in analogy to dynamic NMR studies. The accelerating effect on the rate of enantiomerization of electron-donating groups in the para positions and the decelerating effect of electron-accepting groups has been determined. Dynamic gas chromatography is shown to be a useful supplement to studies of thermal enantiomerization kinetics of optically enriched or separated compounds by polarimetry for the investigation of energy barriers of atropisomeric biphenyls.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199505114
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