  Water exchange reactions around ionic solutes are ubiquitous in aqueous
solution-phase chemistry. However, the extreme sensitivity of exchange rates to
perturbations in the chemistry of an ionic solute is not well understood. We
examine water exchange around model ions within the language of dynamic
facilitation theory, typically used to describe glassy and other systems with
collective, facilitated dynamics. Through the development of a coarse-grained,
kinetically-constrained lattice model of water exchange, we show that the
timescale for water exchange scales exponentially with the strength of the
solute-solvent interactions.
