Asymmetric binding of symmetric guests in a water-soluble cavitand

Abstract

Binding of long aliphatic chains in water-soluble container compounds is driven by the hydrophobic effect: the CH2 groups of the guests are buried from water and solvate the inner aromatic surface of the host. The hydrophobic forces and the CH-π attractions are often sufficient to contort the guests into otherwise unfavorable shapes. Here we show that alkanes, α,ω-diols, α,ω-diacids and their methyl esters assume folded, J-shaped conformations in a water-soluble cavitand. The environment of the guest’s ends interconvert rapidly on the NMR timescale through yo-yo like motions. The applications of water-soluble cavitands to reaction processes are discussed in the context of moving vs. fixed guest ends.