Reaction rates of O + CH3Br and O + CH3Cl

Rate constants for the reaction O + CH3X → CH2X + OH (X=Br,Cl) have been measured over a wide temperature range using a discharge flow reactor, with pseudo-first-order decays of CH3X measured mass spectrometrically. The Arrhenius expresssion k (O+CH3Br) = 3.5×1013 exp(−4560/T) cm3 mole−1⋅sec−1 was obeyed over the range 500°–1000°K with a probable error of about ±20%. Direct measurements of the ratio k (O+CH3Br)/k (O+CH3Cl) showed the two rate constants to be equal within experimental error (±10%) over the same temperature range. Comparisons with literature data are made.