AbstractThe rate constants for the reactions Cl + CH3OD → CH2OD + HCl (1) and CH2OH + O2→ HO2+ H2CO (2) have been determined in a discharge flow system near 1 torr pressure with detection of radical and molecular species using collision‐free sampling mass spectrometry. The rate constantk1, determined from the decay of CH3OD in the presence of excess Cl, is (5.1 ± 1.0) × 10−11cm3s−1. This is in reasonable agreement with the only previous measurement ofk1. The CH2OH radical was produced by reaction (1) and its reaction with O2was studied by monitoring the decay of the CH2OH radical in the presence of excess O2. The result isk2= (8.6 ± 2.0) × 10−12cm3s−1. Previous estimates ofk2have differed by nearly an order of magnitude, and our value fork2supports the more r