Formation constants, K , and single ion conductances, A,, of complexes of Na+ and K+ with a series of 4'-substituted monobenzo-15-crown-5 and monobenzol8-crown-6 ligands were determined conductometrically in acetone at 25 OC. For the complexes of Na+ with benzo-15-crown-5 ligands a 25-fold difference in K is observed between the 4'-amino and 4'-nitro derivative. A good Hammett correlation is found by plotting log K vs. up-+ u, for nine 4'-derivatives, the p value being -0.45. The substituent effect in Na+/benzo-l8-crown-6 complexes is much smaller, and almost negligible for electron withdrawing substituents. No Hammet correlation is found. It is argued that in this system the pronounced difference in the diameters of cation and crown cavity causes the distance between the cation and the aromatic oxygen atoms to change as a function of the nature of the substituent, which in turn can induce conformational changes in the polyether ring. Substituent effects are somewhat larger for K+/benzo-18-crown-6 complexes, but again no linear Hammett plot is obtained. In mixtures of K+ with monobenzo-15-crown-5, 1:l and 2:l crown-cation complexes can exist simultaneously, and, although no K values could be calculated, substituent effects on the complexation are quite pronounced.

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Aus dem Dihydroxybenzaldehyd (I), n‐Butanol und den Äthern (II) entstehen die Kronenäther (IIIa).