Solvent extraction of alkali metal cations from aqueous solutions by highly lipophilic crown ether carboxylic acids

Competitive solvent extractions of alkali metal cations from water into chloroform by 2-(sym-dibenzo-16-crown-5-oxy)-butanoic acid (5), 2-(sym-dibenzo-16-crown-5-oxy)hexanoic acid (6), 2-sym-dibenzo-16-crown-5-oxy)octanoic acid (7), 2-(syn-dibenzo-16-crown-5-oxy)decanoic acid (8), and 5-(sym-dibenzo-16-crown-5-oxy)pentanoic acid (9) are reported. For 6, 7, and 8 the complexing agents are sufficiently lipophillic that they remain totally in the organic phase when chloroform solutions of the crown ether carboxylic acids are contacted with highly alkaline aqueous alkali metal salt solutions.