The Mercury Photosensitized Reaction of Dimethyl Ether

The mercury photosensitized reaction of dimethyl ether has been investigated at pressures between 28 and 500 mm and at temperatures between 25°C and 292°C. At 25°C the products consist almost entirely of hydrogen and 1,2‐dimethoxyethane, and the initial step has been shown to be the abstraction of a hydrogen atom. At higher temperatures CH₂O, CH₄, C₂H₆ and probably CH₃OC₂H₅ become important products. They are derived from the decomposition of the methoxy methyl radical followed by subsequent radical recombination reactions. Carbon monoxide is produced in the later stages from the decomposition of formaldehyde. By varying the light intensity and pressure it has been shown that ethane and dimethoxyethane are produced by second order recombination of methyl and methoxy methyl radicals respectively. The activation energies of the following reactions have been estimated: $$\begin{array}{cc}{\mathrm{CH}}_3+{\mathrm{CH}}_3{\mathrm{OCH}}_3\to {\mathrm{CH}}_4+{\mathrm{CH}}_3{\mathrm{OCH}}_2& \text{E=9.0\hspace{0.17em}}\mathrm{kcal}.\\ \mathrm{\hspace{0.17em}\hspace{0.17em}}{\mathrm{CH}}_3{\mathrm{OCH}}_2\to {\mathrm{CH}}_3+{\mathrm{CH}}_2\mathrm{O}& \text{E=19\hspace{0.17em}}\mathrm{kcal}.\end{array}$$ the only assumption being that methyl and methoxy methyl radicals recombine with zero activation energy.