Separation isomeric

Compounds 39 were prepared by the alkylation of benzotriazoles with the eorresponding diarylmethyl ehloride and the mixtures of isomers were subsequently ehromatographieally separated. Isomerizations were earned out by heating pure dry samples of either 39a or 39b at 175-250°C and the ratios were estimated from the NMR signal intensities. The attainment of thermodynamie equilibrium was eonfirmed by the almost-identieal ratios of 39a and 39b obtained by heating either of the isomers [90JCS(P2)2059]. Table VI summarizes the results of isomerization of eompounds 39. 

Gray, M., Dennis, G.R., Wormell, P., Shalliker, R.A., Slonecker, P. (2002). Two-dimensional reversed phase separations isomeric separations incorporating C18 and carbon clad zirconia stationary phases. J. Chromatogr. A 975, 285-297. 

Condensation of 2-ethynylcyclohex-l-eneylcarbaldehyde 69 with an excess of acetone gave the ketone 544 Reaction of equimolar amounts of 85 and 86 in ethereal methanolic potassium hydroxide gave the ketone 87. Oxidative coupling of 87 under Glaser conditions afforded two separable isomeric bisdehydro[15]-annulenones 88 and 89. The mono-ds isomer 88 may have the structure 90 in which... 

Although the energy barriers separating isomeric carbonium ions are not known and depend strongly on the nature of the attached anions, the relative rates of carbonium ion rearrangements can be estimated from... 

The desired C8A isomer is separated out from the full blend. Depending on the isomer, this separation may be done by fractionation, by crystallization, or by selective absorption (see Chapters 5-7). Whatever the method, the separation of that species leaves a mixture depleted in the desired isomer. C8A isomerization technology converts that mixture back to an equilibrium or near-equihbrium mixture, which is then fed back into the separation unit within the separation-isomerization loop. In this way, the full range of C8 aromatics can be converted to extinction to the desired end-product. Although EB could also be separated from the C8A mixture, this is usually too costly, so EB is typically generated by the... 

Since thexylborane reacts about 100 times faster with Z alkenes than with the corresponding E isomers, it may also be used to separate isomeric mixture.348... 

Administration of separate isomeric forms of BHC (a, 6) produced liver tumors and lung metastases in mice, whether bred for a low or high incidence of spontaneous tumors (ref. 100). Effects of BHC reported on exposed humans Include liver cirrhosis and chronic hepatitis in 8 workers also cases of aplastic anemia and leukemia (ref. 100, p. 157). Animal studies to date focused primarily on the reproductive effects of lindane are both insufficient and inconclusive. Earl et al. reported fetotoxic effects (stillbirths, perinatal deaths) in beagles (ref. 

A sequential process involving a copper catalyzed cycloaddition of the vinyl sulfone 34 to Af-methylpropargylamine (35), and a subsequent palladium meditated allylic substitution, provided a route to mixtures of the separable isomeric pyrrolines 36 and 37 <02EJO1493>. 

Hydroxymethyl-4-methyl steroid derivatives (177) have been prepared from 4-en-3-ones (173) by reductive methoxycarbonylation (Li-NH3, C02, then methylation with CH2N2), followed by methylation of the /3-keto-esters (175) and finally reduction with LiAlH4 to give separable isomeric diols (177).165... 

In this paper, we present experimental data on the above types of stationary phases, in order to evaluate the stereoselective properties of these phases and the possibilities of separating isomeric substances that are otherwise difficult to separate by current analytical procedures ... 

Hash chromatography was introduced by Still, Khan and Mitra in 1978.1 It as cut down the time taken for routine purification of reaction mixtures considerably and, perhaps more importantly, has provided the chemist with i. fast and simple technique for separating isomeric materials which have iimilar polarities. It has become the standard method of purification in any synthetic laboratories, with a resultant reduction in the time taken to jchieve many synthetic goals. 

Szilard-Chalmers reactions are of special interest for the investigation of nuclear isomers, because they offer the possibility of separating isomeric nuclides. 

The steric orientation of the functional groups in the solute molecule in relation to the spatial arrangement of the hydroxyl groups on the surface enable silica and alumina to separate isomeric components (e.g. cis-trans/positional isomers). 

CE amol-fmol Separation, profiling Rapid separation, isomeric resolution, small sample volume Limited databases for CE, standards required for structural annotation, limited compatibility with MS... 

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