[Interaction between acyclic phenol--formaldehyde oligomers and quaternary ammonium ions]

The interaction between acyclic phenol-formaldehyde oligomers (1) and quaternary ammonium ions (5) was investigated by 1H-NMR spectroscopy. From the induced chemical shift change of 5 in the presence of 1, the cation-pi interaction between the N(+)-(CH3)3 moiety of 5 and the pi-base of 1 occurs during the formation of the complex. Another important observation is that the OH proton signals of 1 are considerably broadened upon addition of 5, indicating that hydrogen bonding occurs between exchangeable protons of 1 and iodide anion of 5. These interactions play an important role in the binding of 5.