N-[ω-(Long-chain alkyl)oligo(oxyethylene)] monoaza crown ethers (Cx.(m + l)-N(15, 18), x: 8 and 12, m: 0~2) were prepared from alkyl oligo(oxyethylene) chlorides and N-unsubs-tituted monoaza crown ethers (Scheme 1). From the measurements of cloud points, it was found that the introduction of oxyethylene units between monoaza crown ring and alkyl moiety increased the hydrophilicities compared with those in the N-alkyl monoaza crown ethers (Cx.-N(15, 18), x: 8 and 12) (Table 2). Most of the changes in the cloud points (ΔTCP) of Cx;.E(m + l)-N(15, 18) and Cx-N(15, 18) between the absence and the presence of metal chlorides showed “positive” values (Fig. 1, 2 and Table 3), and it was found that ΔTCP of these compounds as well as alkyl crown ethers depended on such factors as the size of the crown ring, the number of oxygen atoms in the side chain and the kind of metal cations. On the other hand, complexing stability constants (log K1') for these monoaza crown compounds with Na+ and K+ in methanol and in water/methanol (10: 90 v/v) mixture at 25°C were measured by Frensdorff's method. It was observed that the stability constants for CxE.(m + l)-N(15, 18) having oxygen atoms in the side chain were much higher than those for Cx;-N(15, 18) with both cations (Table 4). These results show that the oxygen atoms in the side chain make a remarkable contribution to the complexation with metal cations. Besides, a good correlation between ΔTCP and log K1' was observed (Fig. 3) and it was indicated that ΔTCP was able to be an index of complexing abilities for these monoaza crown compounds with metal cations in water.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)