  We investigate the role of carbon monoxide ice in the chemical evolution of
prestellar cores using astrochemical rate equation models. We constrain the
ratios of the binding energies on CO ice and H$_{2}$O ice for a series of
adsorbates deemed important in diffusive chemistry on H$_{2}$O ices. We later
include these ratios in our chemical reaction network model, where the binding
and diffusion energies of icy species vary as a function of the surface
composition. When the surface coverage of CO increases, the model shows an
enhancement of O-bearing complex organic molecules, especially those formed
from the intermediate products of CO hydrogenation (e.g. HCO) and
CH$_{3}$/CH$_{2}$. Because the binding energy of CH$_{3}$/CH$_{2}$ is in the
right range, its diffusion rate increases significantly with CO coverage. At
$T>$14 K and with less influence, enhanced diffusion of HCO also contributes to
the increase of the abundances of COM. We find, however, that chemistry is not
always enhanced on CO ice and that the temperature and cosmic ray ionization
rate of each astronomical object is crucial for this particular chemistry,
revealing a highly non-trivial behavior that needs to be addressed on a
per-case basis. Our results are highly relevant in the context of interstellar
ice observations with JWST.
