Observation of an H/D‐isotope exchange channel in the reaction D + H₂CO

The reactions of H and D atoms with H 2 CO, H + H 2 CO → H 2 + HCO , (1) D + H 2 CO → HD + HCO , (2a) → HD + HDCO , (2b) were studied in an isothermal discharge flow reactor at room temperature with EPR detection of H and D atoms and LIF detection of HCO radicals. Simultaneous measurements of the absolute concentration‐versus‐time profiles of D, H, and HCO in the D + H 2 CO system established the occurrence of the H/D isotope exchange reaction (2b), which competes with the usually assumed direct H atom abstraction channel (2a). The room temperature rate constants of the two reaction channels were found to be k 2a (296 K) = (1.9±0.5) × 10 10 cm 3 /mol s , k 2b (296 K) = (1.5∓0.4) × 10 10 cm 3 /mol s .