Ethers complexation liquid chromatography

The use of chiral stationary phases (CSP) in liquid chromatography continues to grow at an impressive rate. These CSPs contain natural materials such as cellulose and starch as well as totally synthetic materials, utilizing enantioselective and retentive mechanisms ranging from inclusion complexation to Ti-electron interactions. The major structural features found in chiral stationary phases include cellulose, starch, cyclodextrins, synthetic polymers, proteins, crown ethers, metal complexes, and aromatic w-electron systems. 

Fig. 3 Chromatograms obtained by pH zone-refining CCC. (A) Separation of CBZ(Z) dipeptides. Experimental conditions are as follows apparatus type-J multilayer CPC (PC Inc., Potomac, MD, USA) with a 10-cm revolution radius column multilayer coil, 1.6-mm ID, 325 mL capacity solvent system methyl tert-h xiy ether/acetonitrile/water (2 2 3), 16 mM TEA in organic phase (pH 1.83), and 5.5 mM NH3 in aqueous phase (pH 10.62) sample eight CBZ(carbobenzyloxy) dipeptides as indicated in the chromatogram, each 100 mg in 50 mL of solvent (25 mL in each phase) flow rate 3.3 mL/hr in head-to-tail elution mode detection 206 nm revolution 800 rpm retention of stationary phase 65.1%. (B) Separation of bacitracin complex. High-performance liquid chromatography (HPLC) analysis indicated that two major components, bacitracins A and B, were isolated in peaks 3 and 5, respectively. Experimental conditions are as follows apparatus and column same as above solvent system methyl r -butyl ether/ acetonitrile/water (4 1 5), 40 mM triethylamine, 10% DEHPA in the organic stationary phase, and 20 mM HCl in aqueous mobile phase flow rate 3 mL/min sample 5 g of bacitracin dissolved in 40 mL of solvent (20 mL in each phase) revolution 800 rpm detection 280 nm.

This low value was confirmed after isolation of this y-hexalactone from the complex extract by high-performance liquid chromatography [Si02 5 pm 1.5 ml/min pentane-diethyl ether (70 30) RI detection]. The eluate in the interval 15-16 min was concentrated and analysed by multidimensional GC cf. separation conditions. 

Similar slow sorption-desorption kinetics were observed with some other enantioselective phases in liquid chromatography (103-105). Also with highly selective crown ethers or cryptates the release of substrates from their complexes can be extremely slow (A-6). 

Cationic Polymerization of ll-CF-4. Cationic polymerization of ll-CF-4 was carried out with boron trifluoride ether complex in dichloromethane. The progress of the reaction was monitored by gas chromatography and liquid chromatography by using n-tetradecane as an internal standard. In Figure 3 is shown the... 

When the reaction has progressed to the desired stage (Note 6), the flow of air is stopped and the mixture is filtered. After the filtrate has been extracted with two 350-ml. portions of petroleum ether (b.p. 30-60°), the combined hydrocarbon extracts are washed successively with two 100-ml. portions of 2N hydrochloric acid and three 100-ml. portions of water. The petroleum ether is distilled from the solution, heated in a water bath, through a 60-cm. Vigreux column, and the residual liquid is distilled under reduced pressure. The fraction, b.p. 64-65° (1.0 mm.) or 132-134° (35 mm.), is collected as 39.5-52.0 g. (64-85%) of colorless liquid, 1.4846-1.4850. This distillation fraction contains (Note 6) 80-90% of the ci5-cyclododecene (51-76%) accompanied by 10-20% of a mixture of cyclododecane and ai,ira s-l,5-cyclododecadiene (Note 7). If desired, the cis-cyclododecene may be further purified by preparative chromatography or separation of the silver nitrate-olefin addition complex (Note 8). 

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