  The hot Jupiter WASP-12b is a heavily irradiated exoplanet in a short period
orbit around a G0-star with twice the metallicity of the Sun. A recent
thermochemical equilibrium analysis based on Spitzer and ground-based infrared
observations suggests that the presence of $\ch4$ in its atmosphere and the
lack of $\h2o$ features can only be explained if the carbon-to-oxygen ratio in
the planet's atmosphere is much greater than the solar ratio ($\ctoo = 0.54$).
Here, we use a 1-D photochemical model to study the effect of disequilibrium
chemistry on the observed abundances of $\h2o, \com, \co2$ and $\ch4$ in the
WASP-12b atmosphere. We consider two cases: one with solar $\ctoo$ and another
with $\ctoo = 1.08$. The solar case predicts that $\h2o$ and $\com$ are more
abundant than $\co2$ and $\ch4$, as expected, whereas the high $\ctoo$ model
shows that $\com$, C$_{2}$H$_{2}$ and HCN are more abundant. This indicates
that the extra carbon from the high $\ctoo$ model is in hydrocarbon species.
$\h2o$ photolysis is the dominant disequilibrium mechanism that alters the
chemistry at higher altitudes in the solar $\ctoo$ case, whereas
photodissociation of C$_{2}$H$_{2}$ and HCN is significant in the super-solar
case. Furthermore, our analysis indicates that $\c2h2$ is the major absorber in
the atmosphere of WASP-12b and the absorption features detected near 1.6 and 8
micron may be arising from C$_{2}$H$_{2}$ rather than $\ch4$. The Hubble Space
Telescope's WFC3 can resolve this discrepancy, as $\c2h2$ has absorption
between $1.51 - 1.54$ microns, while $\ch4$ does not.
