Dominant reactions controlling the abundance of CO, H₂O, and SiO under warm (T_K ≥ 800 K) and irradiated conditions. OH appears to be a key intermediate for the three species. The ionization state of carbon controls the destruction of SiO and H₂O as well as the formation of CO. The ionization state of silicon controls the formation of SiO. For an unshielded ISRF FUV radiation field, carbon and silicon are ionized for n_H ∕G₀ ≲ 10⁵ cm⁻³ and n_H ∕G₀ ≲ 3 × 10⁶ cm⁻³, respectively.