Industrial macrocyclic extractants

Low Voltage Mass Spectrometry of Macrocyclic Extractables. Nominal parent mass analyses of the macrocyclic extractables, obtained from typical polymerization products of cyclooctene and 1,5-cyclooctadiene, were performed on a Model MS-9 double focusing mass spectrometer (Associated Electrical Industries, England) at a resolution of 1/1000 and an emission of 7.0 e.v. Samples were introduced directly into the source chamber by the direct-probe technique. The temperature range during the experiment was 125°-200°C., and the source pressure was maintained in the 0.1-3 X 10-6 torr range. In addition, a high resolution measurement was carried out on the mass number 220 to identify the two components present at that mass number. 

Liquid-liquid extraction techniques are used in some cases for the industrial separation, concentration and recovery of metals. Introduction of sulfur into the polyether macrocycles has increased the selectivity of those compounds toward the thiophilic metal ions such as Ag", Hg , Au" and Pd" . 

In the case of clathrates and adducts described earlier, the so-called compounds formed are separated by crystallization. Although handling of slurry/soUd in an industrial context is sometimes not desired, the solid phase conclusively demonstrates the nature of the non-stoichiometric dissociable host-guest compound formed. That macrocyclic ethers form reasonably stable complexes has also been demonstrated by the isolation of the complexes as crystals (Pedersen, 1988). That a particular crown ether having a certain cavity diameter will prefer a certain alkali metal cation having a certain diameter is illustrated in Table 4.1.12 for the extraction of a particular alkali metal picrate salt from water into methylene chloride containing the crown ether. From the table it appears that potassium picrate is most effl-ciently extracted by 18-crown-6 compared to other crown ethers, since the cavity size of 18-crown-6 is quite close to that of (see Table 4.1.11). 

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