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Extent of H–D exchange effects between methanol and water on CH3OD

Quantify the extent to which thermal H–D exchange between methanol (CH3OH/CH3OD) and water (H2O/HDO/D2O) in warm ices (≥120 K) modifies the D/H ratio of hydroxyl-deuterated methanol (CH3OD) inherited from prestellar ices.

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Background

H–D exchange between the OH group of methanol and water occurs at temperatures as low as ~120 K and can alter CH3OD and CH3OH abundances during protostellar warm-up.

Because H2O is generally much more abundant than CH3OH, exchange reactions can substantially impact CH3OD, but the magnitude of this alteration remains unquantified.

References

It is thus likely that this mechanism leads to changes in the D/H ratio of prestellar CH$_3$OD, but the extent of this alteration is unknown.

— First Detection of CH3OD in Prestellar Cores (2511.03581 - Kulterer et al., 5 Nov 2025) in Section 5.2 (Survival of Prestellar D/H Ratios in Methanol)