  Recent surveys of protoplanetary disks show that substructure in dust thermal
continuum emission maps is common in protoplanetary disks. These substructures,
most prominently rings and gaps, shape and change the chemical and physical
conditions of the disk, along with the dust size distributions. In this work,
we use a thermochemical code to focus on the chemical evolution that is
occurring within the gas-depleted gap and the dust-rich ring often observed
behind it. The composition of these spatial locations are of great import, as
the gas and ice-coated grains will end up being part of the atmospheres of gas
giants and/or the seeds of rocky planets. Our models show that the dust
temperature at the midplane of the gap increases, enough to produce local
sublimation of key volatiles and pushing the molecular layer closer to the
midplane, while it decreases in the dust-rich ring, causing a higher volatile
deposition onto the dust grain surfaces. Further, the ring itself presents a
freeze-out trap for volatiles in local flows powered by forming planets,
becoming a site of localized volatile enhancement. Within the gas depleted gap,
the line emission depends on several different parameters, such as: the depth
of the gap in surface density, the location of the dust substructure, and the
abundance of common gas tracers, such as CO. In order to break this uncertainty
between abundance and surface density, other methods such as disk kinematics,
become necessary to constrain the disk structure and its chemical evolution.
