Poly(p-tert-butyldimethoxydipropyloxycalix[4] arene--tetramethyldisiloxane) (TBCX-TMDS) and poly (dimethoxydipropyloxycalix[4]arene-tetramethyldisiloxane) (CX-TMDS), have been prepared and used as stationary phases for isothermal capillary gas chromatographic separations of positional isomers. Retention factors and separation factors for the isomers were measured. The isomers investigated were well-resolved on the two phases. Retention of all the solutes investigated is greater on TBCX-TMDS than on CX-TMDS, probably because of extra dispersive interactions of the solutes with the tert-butyl groups of the phase. Separation factors for closely-eluting isomer pairs are similar on the two phases. This seems to indicate either that the solutes are retained by non-inclusion processes or that if the isomer molecules do enter the cavity of the calixarene, i.e. the solute is retained by inclusion, the tertbutyl groups do not play a role in discriminating between the isomers.

Column liquid chromatography Interaction of mobile and stationary phases Linear solvation energy relationships Triethylamine SummaryThe effect of triethylamine (TEA) in the mobile phase on the RPLC retention behavior of small organic solutes has been studied on a conventional polymeric octadecylsilica (ODS) and on a horizontally polymerized ODS. Retention factors for a set of solutes were measured on the two phases with methanol-water mobile phases containing triethylamine at different concentrations and analyzed by use of linear solvation energy relationships (LSER). Variation of the resulting LSER coefficients -v (hydrophobicity), r (polarizability), s (dipolarity), b (hydrogen-bond (HB) donating acidity), and a (HB accepting strength) -were examined to see how TEA affects the intermolecular interaction properties of the mobile and stationary phases and hence the retention of the solutes. Addition of TEA to the mobile phase changes the interaction properties of both conventionally polymerized and horizontally polymerized ODS; the effect is greater for the conventional phase. The HB donating acidity (b) of conventional polymeric ODS is significantly reduced by addition of TEA. For the mobile phases studied the magnitudes of the b and v coefficients for the horizontally polymerized ODS phase are greater than for the conventional phase. The different interaction properties of the two polymeric phases arise mainly as a result of differential adsorption of TEA, because of the very different amounts of surface silanol groups present on the two phases.

SelectiveReduction of Carbonyl Compounds with Al-Alkoxydiisobutylalanes.-The title alanes, e.g. iBu 2 Al-O-Et, only reduce aldehydes and ketones such as (I), (III), (V), and (VII), whereas esters, nitriles and acid chlorides are not attacked. Highly chemoselective discrimination between structurally different ketones, c.f. (IX)/(X), between aldehydes and ketones, c.f. (Ia)/(Id), and between aldehydes, c.f. (Ib)/(XIII), is possible. Stereoselective reductions are achieved using iBu 2 Al-O-iPr. -(CHA, J. S.; KWON, O. O.; KIM, J. M.; CHUN, J. H.; LEE, Y. S.; LEE, H. S.; CHO, S. D.; Bull.

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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.