Synthesis Of Methoxy12-Crown-4Derivatives And Study On Their Double Selectivity For Alkali And Transition Metals

Crown ethers have always attracted particular attention due to their excellent complex selectivities, different crown ethers have different complexing ability of metals.12-crown-4has exceptional selectivity for lithium ion, because its cavity size is close to that of lithium ion.12-crown-4is becoming an excellent chemical reagent in the study of separating and analyzing for lithium ion. By the introduction of different constituents on the12-crown-4framework, not only does its solubility property change, but also its application scope improves. Based on this idea,2-[(6-bromohexyl)oxy]methyl-12-Crown-4and2-[(12-bromodecyl)oxy]methyl-12-Crown-4are synthesized by2-(hydroxym-ethyl)-12-crown-4when DMF works as solvent and KH as a catalyst.2-[(12-Mercaptohexyl)oxy]methyl-12-crown-4is further synthesized when2-[(6-bromohexyl)oxy]methyl-12-Crown-4reacts thiourea. Their composition and structural configuration are characterized. Under different pH conditions, the extraction of alkali metals Li, Na for the three compounds is determined. Result shows both2-[(6-bromohexyl)oxy]methyl-12-crown-4and 2-[(12-bromodecyl)oxy]methyl-12-Crown-4have a good Li+complexation. They coordinate lithium in1:1ratio and their lithium extraction increase as pH goes higher, leveling off at a certain pH values. This Extraction behavior expands their scope of application. However, the extraction ability is against that of2-[(12-Mercaptohexyl)oxy]methyl-12-crown-4. Both of them demonstrate poor extraction efficiency for sodium (the extraction is close to6.62%in max.), revealing that crown ether can be used as intermediates in synthesizing new materials due to the special role of the lithium ion.Since cadmium ion is soft Lewis acid and affinity to Lewis base, this paper systematically examined cadmium-ion extraction by the same crown ether. The result shows that the diluting reagent has great influence on the extraction of cadmium ion. When the dielectric constant of solvent is small, the extracting rate of cadmium by crown ether is only2%. In contrast, the nitrobenzene with strong polarity, its extract rate can reach63%. Acidity and extraction time have a great influence on the extraction efficiency.The extracting rate of cadmium-ion by crown ether can reach70%, so it is necessary to further investigate the extraction of other heavy metals by this type crown ether.