Li-selective calix[4]arene with trialkyl-monoacetic acid groups: effect of three alkyl branches and t-octyl groups at p-position on selectivity for Li extraction
摘要
Trialkyl-monoacetic acid derivatives of p–t-octylcalix[4]arene and calix[4]arene were prepared to investigate the effect of the alkyl branches attached to the phenoxy oxygen atoms and the p-position on the selective extraction of Li+ over Na+. Alkyl branches on the phenoxy oxygen atoms remarkably affected the Li+ selectivity, whereas those at the p-position had less effect. The former can contribute to excluding Na+ extraction while enabling Li+ extraction. Optimal selection of the alkyl branch improves the Li+ selectivity of calix[4]arene. However, sterically-hindered p–t-octylcalix[4]arene with three 2-ethylbutyl branches exhibited opposite selectivity.