Self‐Diffusion Coefficient and Apparent Molar Volume Studies of Crown Ethers in Aqueous (D2O) and CDCl3 Solutions

Abstract

AbstractWe have measured the self‐diffusion coefficient and density properties of 15‐crown‐5 and 18‐crown‐6 ethers in aqueous (D2O) and CDCl3 solutions in the range of 0 to 6 m concentration of ethers. Some measurements for 1 m crown in D2O with various concentrations of alkali‐metal bromides are also reported. It has been observed that self‐diffusion coefficients of the crowns are small and decrease with increase in concentration of the crown both in D2O and CDCl3 solutions. The density data in D2O were used to obtain the apparent molar volumes of the crown φv as a function of concentration. It has been observed that φv goes through a minimum at about 2 m of crown concentration. Similar measurements and calculations of 1 m crowns in D2O in various salt solutions indicate that D varies peculiarly as a function of salt concentration. 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 volumes of the salts calculated in 1 m 18‐crown‐6 and 1 m 15‐crown‐5 solutions exhibit anomalous dependence on salt concentration. These results are explained on the basis of solute‐solute, solute‐solvent, ion‐crown and ion‐ion interactions in solution phase.