Type I Chiral Stationary Phases

These stationary phases were based on aromatic re-acid (3,5-dinitrobenzene) and re-base (a naphthalene moiety) derivatives. In addition to re-re interaction sites, they have hydrogen-bonding and dipole-dipole interaction sites provided by an amide, urea or ester moiety. By nuclear magnetic resonance measurements in solution, three interactions are proposed to occur in the more favoured diastereomeric complex between an N-(3,5-dinitrobenzoyl)-a-amino amide and an N-(2-naphthyl)-a-amino ester: a re-donor-acceptor interaction and two hydrogen-bonding interactions, as shown in Figure 3. In the development of these stationary phases, the reciprocality concept was introduced as follows: if optically active A resolves the enantiomers B, then optically active B resolves the enantiomers of A. As a result, re-acid and re-base compounds have been separated using chiral stationary phases based on re-base and re-acid derivatives. Since a combination of simultaneous re-re and hydro gen-bonding interactions in the nonpolar solvent used as the mobile phase play an important role in chiral recognition, as described above, these stationary phases are mainly used in the normal-phase mode, although it is possible to separate some enantiomers in the reversed-phase mode.

Recently, chiral stationary phases based on the macrocyclic antibiotics, vancomycin and teicoplanin, have been developed. These stationary phases can separate many enantiomers in both normal- and reversed-phase modes.

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Solar Panel Basics

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