Resorcin [4]arene 1 differs from 2 only in the absence of alkyl substituents in the lower rim. Apparently, the substituents play a key role in Cl -transport across the lipophilic membrane, likely by surrounding the anion. On the other hand, alkyl substituents alone do not grant resorcin [4]arenes any significant anion transport ability, as shown by 6 and 7. Due to the lack of nitro substituents in the upper rim, the latter two compounds have much lower dipole moments and much weaker chloride affinity than 2; apparently too low to extract anions from the aqueous phase.