  Methyl isocyanate (CH3NCO) is one of the important complex organic molecules
detected on the comet 67P/Churyumov-Gerasimenko by Rosetta's Philae lander. It
was also detected in hot cores around high-mass protostars along with a recent
detection in the solar-type protostar IRAS 16293-2422. We propose here a
gas-grain chemical model to form CH3NCO after reviewing various formation
pathways with quantum chemical computations. We have used NAUTILUS 3-phase
gas-grain chemical model to compare observed abundances in the IRAS 16293-2422.
Our chemical model clearly indicates the ice phase origin of CH3NCO.
