Dinitrobenzoylated-aminopropyl-silica

Figure 12.1 Dinitrobenzoylated-aminopropyl-silica. This phase is prepared by a catalysed reaction of 3,5-dinitrobenzoic acid with aminopropyl-silica. Retention takes place through charge transfer interactions when an analyte containing an electron-rich n-electron system interacts with the electron-deficient dinitrobenzoyl- system.

Pirkle DNPG (/ )-N-3,5-Dinitrobenzoyl-phenylglycine covalently bonded to aminopropyl silica. 

Column A 30 X 4.6 L-column (porous silica gel with internal surfaces coated with octade< l groups and external surfaces coated with glycerylpropyl groups) (Chemical Inspection and Testing Institute, Tolqro) B 250 X 4.6 Sumichiral OA-2500S ((R)-N-(3,5-dinitrobenzoyl)-1-naphthylglycine bonded to aminopropyl silica) (Sumika, Osaka)... 

A commercially packed h.p.l.c. column (25 cm x 4.6 mm) of y-aminopropyl silanised silica [e.g. 5/mi Spherisorb (Regis Chemical Co.), or 7/im Zorbax (Dupont Co.), or 10 /im Lithosorb (Merck), or 5 m irregular (J. T. Baker Chemical Co.)] was sequentially treated, at a pumping rate of 2 ml/min, with the following solutions 2 ml of triethylamine in 40 ml of dry tetrahydrofuran, 2g of (R)-JV-(3,5-dinitrobenzoyl)phenylglycine in 40 ml of dry tetrahydrofuran, 20 ml of dry tetrahydrofuran, and finally 10 per cent propan-2-ol in hexane, until the base line stabilises. The chiral amino acid derivative (which is available from Aldrich Chemical Co.) becomes ionically bonded to the amino residues on the stationary phase. 

Other types of CSPs, known as brush type, have been constructed synthetically. A chiral structure, usually an amide, is linked to silica by a tether molecule. This approach has the potential for design of the chiral recognition elements. The ability to synthetically manipulate the structures also permits investigation of the role of specific structural elements in chiral selectivity. Several synthetic CSPs were developed by W. H. Pirkle and co-workers at the University of Illinois. An important example is the 3,5-dinitrobenzoyl (3,5-DNB) derivative of 7 -phenylglycine, which is attached to silica by aminopropyl tethers (CSP 2). The 3,5-DNB derivatives of several other amino acids (e.g., CSP 4) and diamines have also been explored. ... 

Successively, Wainer et al. [45] employed the tt-acceptor N-(3,5-dinitrobenzoyl)-/ -( - )-a -phenylglycine (CS1), bound to an aminopropyl silanized silica gel through ionic interactions, for the resolution of racemic 2,2,2-trifluoro-l-(9-anthryl)ethanol (5 fj-g) by planar chromatography eluting with n-hexane/isopropanol (9.5 1, v/v). CSl was bound to Zorbax BP-NH2 plates (DuPont, USA) by continuous development with a tetrahydrofuran solution (20 ml) containing 1 g of the chiral selector. 

Retention (hRfi, h/ f2) and Resolution (o ) Data for Racemic 2,2,2-Trifluoro-1-(9-Anthryl)Ethanol on Aminopropyl Silanized Silica Plates Modified with iV-(3,5-Dinitrobenzoyl)-/ -(-)-of-Phenylglycine (CCSP1, lonically Bonded and CSP1, Covalently Bonded)... 

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