Many anions are quite stable in the aqueous phase, but not so much in organic solvents where its necessary to perform some reaction (usually nucleophilic substitutions). I have heard that crown ethers are good phase transfer catalysts that bring ions to the organic phase. 18-crown-6 is used to coordinate to K+KX+ ions and bring them to organic phases.
While the cation can enter the organic phase, how does the anion enter it then? Does the anion simply “tag along” with the crown ether complex? The anion gains no solvation stability in organic phase, so the anion moving from aqueous to organic phase seems unlikely.
How does the phase transfer catalyst ensure migration of anions to the organic phase?
