AbstractThe reaction of OH and OD radicals with ethylene in the presence of 1 atm argon and 6 Torr water vapor was studied in the temperature range 343–1173 K. The results reveal three kinetically separate temperature regions: (1) 343–563 K, where the disappearance of OH radical is dominated by the addition of OH to the double bond of ethylene; (2) 563–748 K, where concurrent reactions of addition, the reverse reaction of addition and H‐atom abstraction is dominant; and (3) 748–1173 K, where H‐atom abstraction is likely the main reaction. The rate for hydrogen abstraction is 2.4 × 10−11exp[(−2104 ± 125)/T] cm3/molec‐s (for OD 2.1 × 10−11exp[(−2130 ± 172)/T] cm3/molec‐s). There was no obvious pyrolysis of ethylene below 1073 K. The study of OD radical with ethylene s