- MACROCYCLES. 32. HOMOLYTIC DEHYDRODIMERIZATION OF CROWN ETHERS
-
The corresponding bis(crown ethers), as well as phenyl- and hydroxy-substituted crown ethers, were obtained by homolytic dehydrodimerization of 12-crown-4, 15-crown-5, and 18-crown-6 in benzene or water.
- Luk'yanenko, N. G.,Lobach, A. V.,Parfenova, M. N.,Lyamtseva, L. N.,Timofeev, O. S.,Gren' A. I.
-
p. 940 - 943
(2007/10/02)
-
- Template Synthesis and Ionophorous Properties of Substituted Crown Ethers towards Alkali-metal Ions
-
A number of alkyl-substituted crown ethers of the type 2-R-12-crown-4, 2-R-15-crown-5, and 2-R-18-crown-6 (R = Me, Et, octyl, decyl, tetradecyl,icosyl, or Ph) have been prepared in relatively good yields by a novel synthetic route employing the metal-ion template effect.The ionophorous properties of these crown ethers with respect to the transport of lithium, sodium, and potassium picrates across a bulk liquid chloroform membrane were measured and have been compared to those of crown ethers already used as ionophores.Substitution of alkyl and phenyl groups on the crown ethers, making them more lipophilic, does not seem to assist the transport of Na+ and K+ as their picrate salts, but rather appears to make the ionophore more susceptible to remain in the chloroform phase, as the chain length increases, and thereby leads to a reduction in transport.Introduction of alkyl and other groups, however, does seem to assist the transport of Li+ as lithium picrate, although the overall rate of transport is considerably slower for Li+ than the rate for Na+.
- Bowsher, Brian R.,Rest, Antony J.,Main, Brian G.
-
p. 1421 - 1426
(2007/10/02)
-
- 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.
- Ikeda, Isao,Yamamura, Shingo,Nakatsuji, Yohji,Okahara, Mitsuo
-
p. 5355 - 5358
(2007/10/02)
-