A (-) MENTHYL BONDED SILICA PHASE FOR CHIRAL SEPARATIONS - SYNTHESIS AND SOLID-STATE NMR CHARACTERIZATION

A new (-)-menthyl bonded silica phase has been prepared by hydrosilati on of a hydride silica intermediate. The hydride silica intermediate: was synthesized by the reaction of a monoalkoxysilane (CH3)(2)SiH(OEt) with silica gel, yielding a relatively high surface coverage (4,4 mu mol/m(2)) of SiH groups, This intermediate was then used successfully in the preparation of a monomeric (-)-menthyl bonded silica phase. The bonded phase produced has been used for the chromatographic separatio n of enantiomers in a reversed phase mode (chiral separations), Solid state C-13 and Si-29 CP-MAS NMR spectroscopy and DRIFT spectroscopy pr ovides valuable information on the structure of the different surface species formed on silica after modification, The surface coverage of t he hydride silica intermediate and of the final bonded silica phase pr oduced ape also determined. It is found that this modification procedu re can exclusively produce a monomeric coverage of SiH groups on the s ilica surface and can further produce a final monomeric bonded organic silica phase for the separation of enantiomers.