title: Enantiomer separation by complexation SFC on immobilized Chirasil-nickel and Chirasil-zinc.
abstract: The use of complexation SFC for enantiomer separation of Lewis base selectands on chiral nickel(II)- and zinc(II)-bis[(3-heptafluorobutanoyl)-10-methylene-(1R)-camphora te] chemically bonded to poly(dimethylsiloxane) (Chirasil-nickel and Chirasil-zinc) and employed as Lewis acid selectors is described. The method is especially suited for less volatile and configurationally labile racemates. The variation of the experimental parameters temperature T, pressure p and density rho of the mobile phase carbon dioxide on the retention factor k, relative retention r and chiral separation factor alpha is studied, providing insights into the mechanisms of chiral recognition under supercritical conditions. For mecoprop methyl ester (methyl 2-(4-chloro-2-methylphenoxy)propanoate) an unusual increase of alpha at increased temperature is observed on Chirasil-nickel. Supercritical carbon dioxide does not inadvertently affect the complexation equilibria between Lewis donor selectands and the Lewis acid metal selectors during complexation SFC.
authors.affiliation: Institute of Organic Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany. volker.schurig@uni-tuebingen.de
authors.forename: V
authors.initials: V
authors.lastname: Schurig
authors.forename: M
authors.initials: M
authors.lastname: Fluck
mesh_terms: D008456:2-Methyl-4-chlorophenoxyacetic Acid / Q000031:analogs & derivatives / Q000302:isolation & purification; D002264:Carboxylic Acids / Q000302:isolation & purification; D002845:Chromatography / Q000295:instrumentation* / Q000379:methods*; D002849:Chromatography, Gas / Q000379:methods; D003505:Cyclodextrins / Q000737:chemistry*; D004952:Esters / Q000302:isolation & purification; D000431:Ethanol / Q000031:analogs & derivatives / Q000302:isolation & purification; D007700:Kinetics; D008956:Models, Chemical; D009281:Naphthalenes / Q000302:isolation & purification; D009532:Nickel / Q000737:chemistry*; D011312:Pressure; D011392:Proline / Q000302:isolation & purification; D012833:Siloxanes / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors; D015032:Zinc / Q000737:chemistry*
chemical_list: D002264:Carboxylic Acids; D003505:Cyclodextrins; D004952:Esters; D009281:Naphthalenes; D012833:Siloxanes; C413283:dimethyl 1,1'-binaphthyl-2',2'-dicarboxylate; C090733:Chirasil-Dex; C403616:1-(2-naphthyl)ethanol; D000431:Ethanol; C008340:mecoprop; D009532:Nickel; D011392:Proline; D008456:2-Methyl-4-chlorophenoxyacetic Acid; D015032:Zinc