SELF-DIFFUSION COEFFICIENT AND APPARENT MOLAR VOLUME STUDIES OF CROWN-ETHERS IN AQUEOUS (D2O) AND CDCL3 SOLUTIONS

We have measured the self-diffusion coefficient and density properties of 15-crown-5 and 18-crown-6 ethers in aqueous (D2O) and CDCl3 soluti ons in the range of 0 to 6 m concentration of ethers. Some measurement s for Im crown in D2O with various concentrations of alkali-metal brom ides are also reported. It has been observed that self-diffusion coeff icients of the crowns are small and decrease with increase in concentr ation of the crown both in D2O and CDCl3 solutions. The density data i n D2O were used to obtain the apparent molar volumes of the crown phi( v) as a function of concentration. It has been observed that phi(v) go es through a minimum at about 2 m of crown concentration. Similar meas urements and calculations of Im crowns in D2O in various salt solution s indicate that D varies peculiarly as a function of salt concentratio n. In case of KBr solutions, D increases initially and goes through a flat maximum at about 1-2 m of KBr concentration. The apparent molar v olumes of the salts calculated in 1 m 18-crown-6 and 1 m 15-crown-5 so lutions exhibit anomalous dependence on salt concentration. These resu lts are explained on the basis of solute-solute, solute-solvent, ion-c rown and ion-ion interactions in solution phase.