The Synthesis and Cation-complexing Ability of Alkyl Crown Ethers
Alkyl-15-crown-5 and alkyl-12-crown-4 were prepared via polyethylene glycol β-haloalkyl ethers in two steps from terminal olefins, and their complexing ability with cations of alkali and alkaline earth metals was measured by using 1H NMR; it was found to be almost identified with that of the corresponding unsubstituted crown ether.A new type of alkyl crown ether with a chloro substituent could also be synthesized according to this method.
Synthesis of Substituted Crown Ethers from Oligoethylene Glycols
A convenient synthetic method for preparing 12-crown-4, 15-crown-5, 18-crown-6, and 21-crown-7 bearing various substituents by intramolecular cyclization of the corresponding substituted oligoethylene glycols in high yields is described.Substituents include modifiable pendent groups such as phenyl and hydroxymethyl, as well as various alkyl groups.Stability constants for the new substituted crown ethers with sodium and potassium ions in methanol were determined by potentiometric titration.The absolute effect of pendent groups on stability constants was insignificant.