  Here we aim to explore the origin of the strong C2H lines to reimagine the
chemistry of protoplanetary disks. There are a few key aspects that drive our
analysis. First, C2H is detected in young and old systems, hinting at a
long-lived chemistry. Second, as a radical, C2H is rapidly destroyed, within
<1000 yr. These two statements hint that the chemistry responsible for C2H
emission must be predominantly in the gas-phase and must be in equilibrium.
Combining new and published chemical models we find that elevating the total
volatile (gas and ice) C/O ratio is the only natural way to create a long
lived, 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 be
released into the gas to enable an equilibrium chemistry under oxygen-poor
conditions. Photo-ablation of carbon-rich grains seems the most straightforward
way to elevate the C/O ratio above 1.5, powering a long-lived equilibrium
cycle. The regions at which the conditions are optimal for the presence of high
C/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 in
disk gaps. This process can thus also explain the (hints of) structure seen in
C2H observations.
