# What is the oxidation state of carbon in cyclic C_2O_3?

As an hypothetical entity, each carbon atom has an oxidation state of $+ I I I$.
Here, I assumed (reasonably) that the oxidation state of oxygen was $- I I$.
Learned later that this is the cyclic anhydride of oxalic acid, i.e. $H {O}_{2} C - C {O}_{2} H$. It has a fleeting existence, and is a gleam in a spectroscopist's eye.