Mechanism of the Photolysis of Ethane at 1470 Å

A complete analysis of the products of the photolysis of ethane at 1470 Å has been carried out. Isotopic analyses of products of the photolysis of C₂H₆+C₂D₆ and of CH₃CD₃ have led to the following conclusions. (1) It is possible to explain the data on the basis that nearly all molecular hydrogen produced in the primary process comes from the end carbon atom. $$\begin{array}{c}{\mathrm{CH}}_3{\mathrm{CD}}_3\to {\mathrm{H}}_2+{\mathrm{CHDCD}}_2^{*},\\ {\mathrm{CH}}_3{\mathrm{CD}}_3\to {\mathrm{D}}_2+{\mathrm{CH}}_2{\mathrm{CHD}}^{*}.\end{array}$$ The HD can be accounted for by the decomposition of excited CHDCD₂^* and CH₂CHD^*. $$\begin{array}{c}{\mathrm{CH}}_2{\mathrm{CHD}}^{*}\to \mathrm{HD}+\mathrm{CHCH},\\ {\mathrm{CD}}_2{\mathrm{CHD}}^{*}\to \mathrm{HD}+\mathrm{CDCD}.\end{array}$$ (2) Other primary processes are $$\begin{array}{c}{\mathrm{CH}}_3{\mathrm{CD}}_3\to {\mathrm{CH}}_3+{\mathrm{CD}}_3,\\ {\mathrm{CH}}_3{\mathrm{CD}}_3\to \mathrm{H}+\mathrm{D}+{\mathrm{CH}}_2{\mathrm{CD}}_2.\end{array}$$ The importance of the latter, relative to the molecular elimination, is about 15:85. (3) Propane and butane arise from ethyl radicals formed by addition of H and D atoms to ethylene. (4) The excited state of ethane has a lifetime smaller than 10^—9 sec.