LE3 .A278 2005

2005

Roscoe, John

Acadia University

Bachelor of Science

Honours

Chemistry

Chemistry

This kinetic study made use of the relative rate method to examine the reaction of atomic bromine with diethyl ether relative to the reaction of atomic bromine with dimethyl ether as well as the reaction of atomic bromine with dimethyl ether relative to its reaction with 2,2,4-trimethylpentane. Reaction mixtures were prepared in a smog chamber used at pressures close to atmospheric and the loss of organic reactants due to reaction with atomic bromine was measured using gas chromatography. The reaction of atomic bromine with diethyl ether was examined relative to the reaction of atomic bromine with dimethyl ether to develop a further understanding of the role of oxygen in the reaction mechanism. It was found that the rate constant ratio for these reactions does not depend on the concentration of oxygen at small concentrations of bromine. The rate constant ratios obtained at 298 K for the reaction of dimethyl ether and diethyl ether with atomic bromine were centered around the limiting value of 13.5 (± 7%) which was obtained in earlier experiments in our laboratory using large concentrations of atomic bromine and large concentrations of oxygen. The reaction of atomic bromine with dimethyl ether was also examined relative to the reaction of 2,2,4-trimethylpentane as a function of temperature. Analysis of this temperature dependence gave an activation energy of 15.9 (± 6%) kJ mol-1 and a preexponential factor of 1.23 x 10-12 (±16%) cm3molecule-1s-1 for the reaction. These results indicate that in order for the reaction of atomic bromine with dimethyl ether to be significantly competitive with the reaction of atomic bromine and ozone, the atmospheric concentration of dimethyl ether would have to be approximately 590 times greater than the concentration of ozone.

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