Results from a C-shock chemical model with shock velocity v_s = 30 km s^-1 and pre-shock gas-phase depletion of 60% (see Sect. 6.2 for details). Top: fractional abundances of gas-phase CH₃CN, HCN, and CN, and grain surface CH₃CN and HCN (indicated by the # prefix) as a function of distance into the shock front. Bottom: profiles of gas temperature (red) and total hydrogen number density (blue) as a function of distance into the shock front.