Experimental and Theoretical Study of the Kinetics and Mechanism of the Reaction of OH Radicals with Dimethyl Ether

The reaction of OH with dimethyl ether (CH3OCH3) has been studied from 195 to 850 K using laser flash photolysis coupled to laser induced fluorescence detection of OH radicals. The rate coefficient from this work can be parametrized by the modified Arrhenius expression k = (1.23 ± 0.46) × 10–12 (T/298)2.05±0.23 exp((257 ± 107)/T) cm3 molecule–1 s–1. Including other recent literature data (923–1423 K) gives a modified Arrhenius expression of k 1 = (1.54 ± 0.48) × 10–12 (T/298 K)1.89±0.16 exp((184 ± 112)/T) cm3 molecule–1 s–1 over the range 195–1423 K. Various isotopomeric combinations of the reaction have also been investigated with deuteration of dimethyl ether leading to a normal isotope effect. Deuteration of the hydroxyl group leads to a small inverse isotope effect. To gain insight into the reaction mechanisms and to support the experimental work, theoretical studies have also been undertaken calculating the energies and structures of the transition states and complexes using high level ab initio methods. The calculations also identify pre- and post-reaction complexes. The calculations show that the pre-reaction complex has a binding energy of ∼22 kJ mol–1. Stabilization into the complex could influence the kinetics of the reaction, especially at low temperatures (