A variety of factors affect the ability of a given column to discriminate between compounds on the basis of shape (shape selectivity). In reversed-phase systems, bonded phases based on monomeric surface modification exhibit low shape selectivity; phases based on polymeric surface modifications exhibit enhanced shape selectivity. Even greater shape specificity Is exhibited by charge-transfer columns, operated In the normal-phase mode. In this work, the retention behavior of electron-acceptor and electron-donor charge-transfer phases was studied for the separation of polycyclic aromatic hydrocarbon Isomers (PAHs), methylsubstituted PAHs, and polychlorinated biphenyl congeners (PCBs). In all cases, planar compounds were retained In preference to corresponding nonplanar analogues.
racemic sulfoxide); mp 74.5 °C (pure S enantiomer); [ ]2^= ~54°( c 1.98, CHClg); lH NMR (CDClg) & 2.40 (s, 3 H), 2.69 (s, 3 H), 7.28-7.55 (AA'BB'm, 4 H); NMR analysis with the chiral shift reagent, (S)-(+)-2,2,2-trifluoro-l-(9-anthryl)ethanol indicated the sulfoxide to be enriched in the S enantiomer (i.e., 30% ee).
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