Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1203870 | Journal of Chromatography A | 2010 | 7 Pages |
Abstract
Fast semipreparative HPLC enantioseparation of four axially chiral biscarbostyrils (4,4â²-bisquinoline-2-ones) using ULMO as a Ï-acidic Pirkle type chiral stationary phase leads to two racemizing pairs (1,2; kobs 1.6 Ã 10â4 and 3.0 Ã 10â4 sâ1 at 28 °C) and two stable ones (3,4). 3 was stabilized by a crown ether linkage from pos. 6 to 6â², and 4 had sterically demanding bromo substituents in pos. 3 and 3â². On-column generated temperature-dependent chromatograms of 1 and 2 were fitted with Auto-DHPLCy2k and DCXplorer. For cpd 2 both programs delivered similar ÎG values of 90 and 93 kJ/mol, well comparable with the 99 kJ/mol calculated with the B3LYP/6-31G (d) procedure. At temperatures of high conversion DCXplorer delivered inconsistent series of rate constants for the more tailing and less resolved tetramethoxy derivative 1. We connect this problem with an almost impossible halfwidth calculation of tailing peak pairs which are weakly resolved. However, this problem could be observed only in the case of tetramethoxy derivative 1. Stochastic generated data of Auto-DHPLCy2k could be used at a lower percentage of conversion only while the theoretical plate model did not deliver useful data at temperatures of very low conversion but fitted well high conversion chromatogram series of 1 and 2.
Keywords
Related Topics
Physical Sciences and Engineering
Chemistry
Analytical Chemistry
Authors
Georg Uray, Sajid Jahangir, Walter M.F. Fabian,