Interstellar space is not empty; it contains gaseous and particulate matter that is concentrated into interstellar clouds. Organic molecules have been detected in the dens regions of these clouds. This has caused great interests as many of the organic molecules may lead to biomolecules. The gas-phase molecules are synthesized from precursor atoms/molecules by rapid exothermic reactions in the gas and on the surface of tiny dust particles of the interstellar clouds followed by desorption reactions to release these molecules back into the gas phase. This project focuses primarily on interstellar CH3NCO which has recently been detected via spectroscopy toward the nebulae Sgr B2. We incorporate chemical reactions of CH3NCO and related species to the well established reaction network for interstellar clouds. We use a computer simulation to calculate the fractional abundance with respect to hydrogen of CH3NCO over an input span of time. We then compare our results with observations and conclude the most important formation and destruction reactions for CH3NCO and related species.