Rate parameters for the reaction of atomic hydrogen with dimethyl ether and dimethyl sulfide

Absolute rate constants for the reaction of atomic hydrogen with dimethyl ether (DME) and dimethyl sulfide (DMS) were obtained using the flash photolysis–resonance fluorescence technique. Under conditions where secondary reactions are avoided, rate constants for the H+DME reaction over the temperature range 273–426 K are well represented by the Arrhenius expression k1=(4.38±0.59)×10−12 exp(−1956±43/T) cm3 molecule−1 s−1. The corresponding Arrhenius expression for the H+DMS reaction over the temperature range 212–500 K is k2=(1.30±0.43)×10−11exp(−1118±81/T) cm3 molecule−1 s−1. The Arrhenius plot for k2 shows signs of curvature, however, and separate Arrhenius expressions are derived for the data above and below room temperature. These results are discussed and comparisons are made with previous determinations which employed flow discharge and product analysis techniques.