Nuclear Magnetic Resonance Studies of Ion-Exchange Resins. I. Effect of Counter Ion

The nuclear magnetic resonance spectra of packed beds containing the cation exchanger Dowex 50W-X8 in water vary with counter ion. Chemical shifts for water protons internal to the resin bead are in the order H+ (lowest frequency) » Zn2+ ≊ Cd2+ ≤ Pb2+ ≊ Mg2+ ≤ Ag+ ≤ Ca2+ ≊ Tl+ ≊ NEt+ 4 ≊ Ba2+ ≊ Li+ ≊ NMe4 + ≊ Sr2+ ≤ NH4 + ≤ Rb+ ≊ K+ ≊ Na+ ≊ NBu4 +. The concentrated electrolyte model of ion-exchange resins is substantiated by generally good agreement between 1) chemical shifts/g equiv./kg for cations in aqueous solutions referred to NH4 + and 2) chemical shifts/g equiv./kg for resin forms referred to NH4 + form resin.