Experimental data on association reactions of H and HO suggest that radiative association involving atomic and diatomic neutral radicals may be considered as an effective mechanism for the production of small neutral molecules in the interstellar clouds. The formation of O occurs in the gas phase via the neutral exchange reaction between O and HO, which is also the main sink for HO in dense regions.
We can see that atomic oxygen takes part both in the production and destruction of HO, so the abundance of HO depends mainly on the H abundance. Then, important chemical pathways leading from HO radicals are:
HO + O → O + H  (1A)  Neutral-neutral
HO + C → CO + H  (2A) Ion-neutral
HO + N → NO + H   (3A)  Neutral-neutral
HO + C → CO + H  (4A)  Neutral-neutral
HO + H → HO + photon  (5A)  Neutral-neutral