The Viscosity Coefficients of 18-Crown-6–Alkali Metal-ion Complexes

Abstract

The viscosities of LiCl, KCl, and CsCl have been measured in water and aqueous solutions containing 0.398 mol/dm3 of 18-crown-6 (CR) at 25 °C. The B-coefficients of the alkali metal chlorides in water have been obtained using the theoretical values of the A-coefficients. The viscosity coefficients of 18-crown-6 itself have been determined in water and methanol. In systems containing crown ether, the viscosity increment due to the complex formed in solutions, Δη[CR–M+]Cl−, has been evaluated by subtracting from the observed viscosity the increment attributed to non-coordinated crown ether and alkali metal chlorides in solutions. The two complex ions, [CR-K+] and [CR-Cs+], have nearly the same values of the B-coefficients, and these values are, in turn, approximately equal to that of 18-crown-6 in water. Measurements done on KCl in methanol containing 18-crown-6 have led to the finding that in methanol, 18-cown-6 and the [CR-K+] ion take effectively the same B-value.

Viscosity Behavior of 18-Crown-6 in Aqueous and Carbon Tetrachloride Solutions at Different Temperatures and at Ambient Pressure

“…The value of the B -coefficient obtained for aqueous 18C6 solutions at 298.15 K (0.8069 dm 3 mol -1 ) is in excellent agreement with the value (0.798 dm 3 mol -1 ) reported earlier from this laboratory . Kawaizumi et al have reported a B -coefficient value of aqueous 18C6 solutions (0.846 dm 3 mol -1 ) at 298.15 K only, which is much more than that of the value obtained in present study. We believe that this may be due to handling of hygroscopic 18C6, which results in the higher B -coefficient value reported, in the said report.…”