Hydrogen isotope exchange and H(D) atom addition reaction of solid formaldehyde on amorphous solid water at low temperatures

Reaction routes when H2CO and D2CO were exposed to the D and H atoms on amorphous solid water (ASW) at 10–20 K, respectively, were studied experimentally by IR spectroscopy. For D + H2CO on ASW, H2CO was converted to HDCO and D2CO by the H-D substitution reactions. Although CD3OD was slightly observed, doubly- and triply-deuterated methanol, CH2DOD and CHD2OD, were not observed. This implies that the D additions to H2CO (formation of deuterated methanol) is a minor reaction route. On the other hand, for H + D2CO, H addition reactions to form CHD2OH proceed significantly as much as conversions to HDCO and H2CO, which evolve to CH2DOH and CH3OH by the further H additions, respectively. Therefore, in this reaction system, two kind of reaction routes for D2CO → HDCO → H2CO → CH3OH and D2CO → CHD2OH are competitive.