We present an ab initio direct dynamics study on the desorption of CO from semiquinone carbon−oxygen species in carbonaceous surfaces. Density functional theory, in particular B3LYP/6-31G(d) level, was used to calculate the potential energy surface information. We found that in the initial stage of the desorption process, the six-member ring of the carbonaceous model opens slightly to let the CO break away, and then closes up to form the five-member ring. Because of low-lying excited estates in the carbon−oxygen complexes, electronic crossing occurs from reactants to products. Transition-state structures were found for the ground-state path, and the activation desorption energy is in excellent agreement with existing experimental data. Transition-state theory was used to calculate the thermal rate constant for desorption of CO in the range of 600−1700 °C. The fitted Arrhenius expression for the calculated rate constants is k(T) = 1.81 × 1017 exp[−47682/T(K)](s-1), which is within the experimental uncertainty for char gasification. In summary, we demonstrate that it is possible to model kinetics of elementary reactions in carbonaceous surfaces.