Alkali metal perchlorate transport

Comparison of the data for the lipophilic diazacrown ethers in Table 2 with that for the analogous crown ether compounds in Table 1 shows that replacement of two oxygen atoms in the macrocyclic ring with NH or NC2H5 units drastically reduces the alkali metal perchlorate transport. Presumably this results from diminished complexation of the hard alkali metal cations by the macrocyclic ligands when two hard oxygen donor sites are replaced by two nitrogen atoms. 

Alkali metal perchlorate transport lariat ether amides, 161-164 lipophilic 18-crown-6 and 15-crown-5 derivatives, 157-160... 

Transport of Alkali Metal Perchlorates by Lipophilic 18-Crown-6 and 15-Crown-5 Derivatives. 

Transport rates of the five individual alkali metal perchlorate species across bulk chloroform membranes by dicyclohexano-18-crown-6 (2) and lipophilic crown ethers 3-8 are recorded in Table 1. In all cases, transport of lithium perchlorate was undetectable. The K /Na and K /Rb transport selectivities calculated from the single species transport rates are also presented in Table 1. 

The transport of alkali metal perchlorates across the bulk chloroform membrane by dicyclohexano-18-crown-6 (2) varies with the nature of the alkali metal cation in the order K >Na >Rb >Cs >Lr. For the 18-crown-6 ring size, strongest complexation of would be anticipated and the transport shows modest K /Na and K /Rb selectivities. For the transport of alkali metal nitrates across a bulk chloroform membrane by 2, an ordering of K >Rb >Na >Cs >Lr has been reported (77). This reversal in the ordering for transport of Na and Rb is attributed to an effect of the co-transported anion upon transport selectivity (75). 

Transport rates for alkali metal perchlorates across bulk chloroform membranes by the lipophilic diazacrown compounds 9-11,14 and 15 are presented in Table 2. In all cases, transport of lithium and cesium perchlorates was undetectable. 

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