On the enantiomerization barrier of atropisomeric 2,2′,3,3′,4,6′-hexachlorobiphenyl (PCB 132)

Schurig, Volker; Glausch, Alexandra; Fluck, Markus

doi:10.1016/0957-4166(95)00290-6

Cited by 65 publications

(28 citation statements)

References 15 publications

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“…After a given enantiomerization time, the former enantiomerization temperature is restored and the enantiomerized fractions are separated in the second part of the column. The enantiomerization barriers of each of the two enantiomers are calculated from the four peak areas a i , the enantiomerization time t, and the enantiomerization temperature T. By single-column stoppedflow gas chromatography, 42 enantiomerization barriers of …”

Section: Enantioselective Stopped-flow Methodsmentioning

confidence: 99%

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Determination of enantiomerization barriers by dynamic and stopped‐flow chromatographic methods

2001

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In recent years, dynamic chromatography and stopped-flow chromatographic techniques have become versatile tools for the determination of enantiomerization and isomerization barriers. Increasing demands for the stereochemical safety of chiral drugs contributed to the rapid development of new techniques. New computer-aided evaluation systems allow the on-line determination of interconversion barriers from the experimental chromatograms. Both dynamic chromatography and stopped-flow chromatography have been applied to the entire range of chromatographic methods (GC, SFC, HPLC, CE).

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Section: Enantioselective Stopped-flow Methodsmentioning

confidence: 99%

“…Schurig et al 42 determined by this method the rotational energy barrier of the atropisomeric PCB 132 (23). After semipreparative HPLC separation, a single enantiomer was subjected to enantiomerization on Chirasil-␤-Dex.…”

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confidence: 99%

Determination of enantiomerization barriers by dynamic and stopped‐flow chromatographic methods

2001

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“…[13][14][15][16] In particular, dynamic chromatography has been used for the determination of kinetic parameters of stereolabile compounds, for example, atropisomers, [17][18][19][20][21][22][23] drugs and drug-related compounds, [24][25][26] compounds with chirotopic nitrogen and sulphur, [27][28][29][30][31][32][33] pheromones, 34 and even organic radicals. 35 In dynamic chromatography, peak profiles are characterized by peak broadening, plateau formation, and eventually peak coalescence.…”

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Fast and precise access to enantiomerization rate constants in dynamic chromatography

Trapp

2006

Chirality

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An analytical solution of the unified equation to evaluate elution profiles of interconverting enantiomers in dynamic chromatography is presented. Rate constants k1 and k(-1) and Gibbs activation energies are directly obtained from the chromatographic parameters (retention times tR A and tR A of the interconverting enantiomers, the peak widths at half height wA and wB, and the relative plateau height hp), and the initial amounts A0 and B0 of the enantiomers without any iterative and time consuming computational step. Therefore, this equation is no longer limited to racemic analytes. The analytical solution presented here was validated by comparison with a dataset of 125,000 simulated elution profiles of enantiomerizations. Furthermore, it was found that the recovery rate from a defined dataset is on average 40% higher using the unified equation compared to evaluation methods based on iterative computer simulation. The new equation was applied to determine the enantiomerization rate constant of 1-n-butyl-2-tert-butyldiaziridine by enantioselective gas chromatography. The activation parameters (DeltaH(double dagger) = 112.6 +/- 2.5 kJ/mol and DeltaS(double dagger) = -27 +/- 2 J/(K mol) were obtained from temperature-dependent measurements between 100 degrees C and 140 degrees C in 10K steps.

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“…Only 19 of these PCBs are chiral compounds configurationally stable at room temperature due to the restricted rotation about the C-C bond with estimated energy barriers between 105-240 kJ/mol, being these PCBs configurationally stable at the working temperatures in CE (normally, between 10 to 607C) due to they are also configurationally stable (energy barriers higher than 100 kJ/mol) at temperatures as high as 3007C, as has been reported by Schurig et al [34,35]. The existence of axial chirality in PCBs molecules is the reason for which they are called atropisomers.…”

Section: Introductionmentioning

confidence: 66%

Comparison of charged cyclodextrin derivatives for the chiral separation of atropisomeric polychlorinated biphenyls by capillary electrophoresis

2003

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Comparison of charged cyclodextrin derivatives for the chiral separation of atropisomeric polychlorinated biphenyls by capillary electrophoresisCharged cyclodextrin (CD) derivatives were used as chiral selectors in electrokinetic chromatography (EKC) for the chiral separation of highly hydrophobic neutral racemates such as atropisomeric polychlorinated biphenyls (PCBs). b-CD-phosphated, b-CD sulfated, succinylated-g-CD (Succ-g-CD) and succinylated-b-CD (Succ-b-CD) were used as anionic CDs. As cationic CD, 6-monodeoxy-6-monoamino-b-CD (b-CD-NH 2 ) was tested for the first time in order to separate PCBs. From the different CD derivatives employed, the best separations were obtained with the cationic CD derivative. Thus, the use of b-CD-NH 2 in phosphate buffer at pH 2.0 containing urea allowed the chiral recognition of eleven PCBs (45, 84, 88, 91, 95, 131, 136, 144, 149, 176, and 197). In this case, the addition of 2 M urea to the buffer solution was crucial to achieve the chiral separation of PCBs. The addition of acetonitrile to 10 mM phosphate buffer (pH 2.0) with 30 mM b-CD-NH 2 and 2 M urea improved considerably the chiral resolution obtained for PCBs 91, 95, 136, 144, 149, and 197 although an increase in the analysis time was also observed. All the results obtained were compared with those previously obtained with the dual CD system carboxymethyl-g-CD/b-CD.

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On the enantiomerization barrier of atropisomeric 2,2′,3,3′,4,6′-hexachlorobiphenyl (PCB 132)

Cited by 65 publications

References 15 publications

Determination of enantiomerization barriers by dynamic and stopped‐flow chromatographic methods

Determination of enantiomerization barriers by dynamic and stopped‐flow chromatographic methods

Fast and precise access to enantiomerization rate constants in dynamic chromatography

Comparison of charged cyclodextrin derivatives for the chiral separation of atropisomeric polychlorinated biphenyls by capillary electrophoresis

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