Lariat ether thioamides, transport

Transport rates for potassium and silver perchlorates across bulk chloroform membrmes by lariat ether thioamides 29-42 are reported in Table 4. Transport of sodium, cadmium and zinc perchlorates was undetectable. 

For the carriers 29-42, the transport of potassium perchlorate was uniformly low or undetectable. On the other hand, the lariat ether thioamides exhibit a propensity for transport of Ag" across bulk chloroform membranes. Thus substitution of the amide oxygen in a dibenzo-16-crown-oxyacetamide by sulfur to produce the corresponding thioamide transforms an effective Na carrier into an efficient Ag" ... 

For alkali metal cation transport across bulk chloroform membranes by lariat ether amides based upon dibenzo-16-crown-5 rings, preorganization of the coordinating side arm over the polyether cavity enhances both the efficiency and selectivity of Na transport. For the corresponding lariat ether thioamides, efficient transport of Ag", but not the alkali metal cations, is observed. In this case, preorganization of the side arm is detrimental which indicates predominant coordination of the soft Ag" with the soft sulfur atom of the thioamide group. 

Transport of Metal Perchlorates by Lariat Ethers Based on Dibenzo-16-crown-5 Compounds with Amide- and Thioamide-Containing Side Arms. 

We have developed efficient syntheses of. /w-(hy(iroxy)dibenzo-16-crown-5 and jyw-(alkyl)(hydroxy)dibenzo-16-crown-5 compounds 17,18). These lariat ether alcohols, in which the alcohol function and a hydrogen atom or alkyl group are attached to the central carbon of the three-carbon bridge serve as platforms for attachment of various potential coordinating groups to provide a variety of other lariat ether compounds. For example, dibenzo-16-crown-5 lariat ethers with pendent amide 19), ester 20) and thioamide (27) groups have been prepared. To further probe the effect of structural variation within lariat ethers, studies of metal perchlorate transport across bulk chloroform membranes by dibenzo-16-crown-5 lariat ethers with oxyacetamide and oxythioacetamide side arms were undertaken. 

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