The surface tension of aqueous solution of ((dodecyloxy)methyl) -18-crown-6 (D) has been measured in the presence of different concentrations of KC1. The surface tension-concentration curves exhibited at least two break points (C¡ and Cn) below the cmc, irrespective of salt concentrations. The total surface excess density of D and potassium complex (DK+) was derived as a function of concentration below C¡ by means of application of the Gibbs equation. Formation of dimers at C¡ was suggested by the surface tension analysis and by the electric conductivity of a bulk solution. It is considered that the dimer capped by two large crown rings grows to a m-mer composed of less then five molecules, followed by formation of micelles at the cmc. The transition of m-mer to n-mer will be accompanied by a change of the mode of interaction between the hydrocarbon tails, from antiparallel side-by-side contact to tail-to-tail contact. From a consideration of the observed limiting area, it was proposed that the crown rings in the saturated surface layer are stacked bimolecularly at water and 0.01 mol/dm3 KC1 surfaces, on the one hand, and that they stand approximately at an angle of 45°in 0.1 mol/dm3 KC1 and at an angle of 90°in 1 mol/dm3 KC1, relative to the surface. It was estimated by application of the Corrin-Harkins relation that the energy of micellar formation increased by 6.2 kJ/mol with introduction of a charge (K+) into a crown head; i.e., micelles of a hypothetical cationic surfactant DK+CT were more unstable than micelles of nonionic D. A cyclization effect of a hexa(oxyethylene) chain was also discussed.
The reactions of [60]fullerene with bis-o-quinodimethane precursors 3, 4, and 5 containing a dibenzo-18-crown-6, 24-crown-8 and 30-crown-10 moiety, respectively, were investigated. Both 3 and 4 provided trans-4 bisadducts 6a and 7a, respectively, as major product, though the selectivity in the latter was lower than that in the former. As minor product, 6b (cis-2) was produced from 3, while 7c (e) as well as 7b (cis-2) were produced from 4. Precursor 5 exclusively afforded e bisadduct 8 without any other regioisomers. These bisadducts showed different ionophoric properties from one another; for instance, 6a and 7b exhibited a high complexing ability toward the K+ ion, while 6b hardly showed complexation with any alkali metal ions. The selectivity coefficients (K(Na,K)(pot)) of 6a and 7b toward K+ over Na+ ion, determined with an ion-selective electrode, were much higher than that of dibenzo-18-crown-6.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.