Synthesis of chromogenic crown ethers and liquid-liquid extraction of alkali metal ions

Yoshiki Katayama, Kazuhide Nita, Masahide Ueda, Hiroshi Nakamura, Makoto Takagi, Keihei Ueno

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52 Citations (Scopus)


New crown ethers carrying a pendent phenolic chromophore were synthesized. These crown ethers, on dissociation of the phenolic proton, provide lipophilic anions which can extract alkali metal cations into 1,2-dichloroethane by forming highly-colored uncharged metal complexes. Structural effects on the extraction were studied for possible use of these crown ethers as extraction-spectrophotometric reagents selective for alkali metals. The following factors are discussed in detail: (i) nature of the crown ether ring (ring size. aza-crown or standard crown ether), (ii) nature of the pendent phenolic group, and (iii) geometry between the crown ether center and pendent phenolic group. 15-Crown-5 or smaller ring-sized reagents favored the extraction of lithium ion when the basicity of the pendent phenolate was relatively high and a six-membered "chelate" ring was possible for the phenolate and the crown ether-bound metal. 15-Crown-5 type reagents were sodium-selective when an eight-membered "chelate" ring was possible between the phenolate and the crown ether-bound metal. 18-Crown-6 type reagents were generally potassium-selective. However, these selectivities were not absolute, and other structural parameters, steric and conformational, must be considered to explain in detail the selectivities of the individual reagents.

Original languageEnglish
Pages (from-to)193-209
Number of pages17
JournalAnalytica Chimica Acta
Issue numberC
Publication statusPublished - 1985

All Science Journal Classification (ASJC) codes

  • Analytical Chemistry
  • Biochemistry
  • Environmental Chemistry
  • Spectroscopy


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