Reactions of Alkoxy Radicals. III. Photolysis of Methyl-d3 Acetate below 100°C

The photolysis of CH₃COOCD₃ has been investigated at 30 and at 90°C at varying initial pressures and light intensities. The following primary steps were shown to occur: $$\begin{array}{c}\text{(1}\mathrm{a}){\mathrm{CH}}_3{\mathrm{COOCD}}_3\mathrm{+hv\hspace{0.17em}\hspace{0.17em}\to }{\mathrm{CH}}_3\mathrm{CO}+{\mathrm{CD}}_3\mathrm{O}\\ \text{(1}\mathrm{b}\mathrm{)\to }{\mathrm{CH}}_3+{\mathrm{CO}}_2+{\mathrm{CD}}_3\\ \text{(1}\mathrm{c}\mathrm{)\to }{\mathrm{CH}}_3+\mathrm{CO}+{\mathrm{CD}}_3\mathrm{O}.\end{array}$$ The following reactions regarding methoxy and methyl radicals have been investigated: $$\begin{array}{c}\text{(3)}{\mathrm{CH}}_3\mathrm{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\to }{\mathrm{C}}_2{\mathrm{H}}_6\\ \text{(6)}{\mathrm{CH}}_3+{\mathrm{CD}}_3\mathrm{O}\mathrm{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\to }{\mathrm{CH}}_3\mathrm{O}{\mathrm{CD}}_3\\ \text{(7)→}{\mathrm{CH}}_3\mathrm{D}+{\mathrm{CD}}_2\mathrm{O}\\ \text{(11)}{\mathrm{CD}}_3\mathrm{O}\mathrm{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\to }{\mathrm{CD}}_3\mathrm{OD}+{\mathrm{CD}}_2\mathrm{O}\\ \text{(16)}{\mathrm{CD}}_3\mathrm{O}+{\mathrm{CH}}_3{\mathrm{COOCD}}_3\to {\mathrm{CD}}_3\mathrm{OH}+{\mathrm{CH}}_2{\mathrm{COOCD}}_3\\ \text{(17)→}{\mathrm{CD}}_3\mathrm{OD}+{\mathrm{CH}}_3{\mathrm{COOCD}}_2.\end{array}$$ A value of about 1.4 was obtained for k₇/k₆ at 30 and 90°C, indicating the activation energy of reaction (7) to be zero kcal. Data obtained for the abstraction reactions (16) and (17) are discussed. Quantitative data have been obtained and are discussed for the disproportionation and recombination reactions of methyl and acetyl radicals.