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Here we aim to explore the origin of the strong C2H lines to reimagine thechemistry of protoplanetary disks. There are a few key aspects that drive ouranalysis. First, C2H is detected in young and old systems, hinting at along-lived chemistry. Second, as a radical, C2H is rapidly destroyed, within<1000 yr. These two statements hint that the chemistry responsible for C2Hemission must be predominantly in the gas-phase and must be in equilibrium.Combining new and published chemical models we find that elevating the totalvolatile (gas and ice) C/O ratio is the only natural way to create a longlived, high C2H abundance. Most of the \ce{C2H} resides in gas with a Fuv/n-gas~ 10^-7 G0 cm^3. To elevate the volatile C/O ratio, additional carbon has to bereleased into the gas to enable an equilibrium chemistry under oxygen-poorconditions. Photo-ablation of carbon-rich grains seems the most straightforwardway to elevate the C/O ratio above 1.5, powering a long-lived equilibriumcycle. The regions at which the conditions are optimal for the presence of highC/O ratio and elevated C2H abundances in the gas disk set by the Fuv/n-gas ~10^-7 G0 cm^3 condition lie just outside the pebble disk as well as possibly indisk gaps. This process can thus also explain the (hints of) structure seen inC2H observations.

Destruction of refractory carbon grains drives the final stage of proto-planetary disk chemistry