Reaction of CF 3 radicals with group IV tetramethyls

Arrhenius parameters have been measured for the abstraction of hydrogen from the C Si, Ge, and Sn tetramethyls:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {k({\rm ml m}^{ - {\rm 1}} {\rm s}^{ - {\rm 1}} )} \hfill & {{\rm for}} \hfill & {{\rm C}({\rm CH}_{\rm 3} )_4 = {{10^{12.0} {\rm e}^{ - 8370} } \mathord{\left/ {\vphantom {{10^{12.0} {\rm e}^{ - 8370} } {RT}}} \right. \kern-\nulldelimiterspace} {RT}}} \hfill \\ {k({\rm ml m}^{ - {\rm 1}} {\rm s}^{ - {\rm 1}} )} \hfill & {{\rm for}} \hfill & {{\rm Si(CH}_{\rm 3} {\rm )}_{\rm 4} = {{10^{11.9} {\rm e}^{ - 7300} } \mathord{\left/ {\vphantom {{10^{11.9} {\rm e}^{ - 7300} } {RT}}} \right. \kern-\nulldelimiterspace} {RT}}} \hfill \\ {k({\rm ml m}^{ - {\rm 1}} {\rm s}^{ - {\rm 1}} )} \hfill & {{\rm for}} \hfill & {{\rm Ge(CH}_{\rm 3} {\rm )}_{\rm 4} = {{10^{11.7} {\rm e}^{ - 7370} } \mathord{\left/ {\vphantom {{10^{11.7} {\rm e}^{ - 7370} } {RT}}} \right. \kern-\nulldelimiterspace} {RT}}} \hfill \\ {k({\rm ml m}^{ - {\rm 1}} {\rm s}^{ - {\rm 1}} )} \hfill & {{\rm for}} \hfill & {{\rm Sn(CH}_{\rm 3} {\rm )}_{\rm 4} = {{10^{11.7} {\rm e}^{ - 7250} } \mathord{\left/ {\vphantom {{10^{11.7} {\rm e}^{ - 7250} } {RT}}} \right. \kern-\nulldelimiterspace} {RT}}} \hfill \\ \end{array} $$\end{document}The rate constants correlate with the proton chemical shift, which is related to a polar effect. In all cases except carbon, a hot‐molecule β‐fluorine rearrangement‐elimination reaction occurs following radical combination:\documentclass{article}\pagestyle{empty}\begin{document} $$ ({\rm CF}_3 {\rm CH}_2 {\rm M}({\rm CH}_3 )_3 )^* \to {\rm CF}_2 {\rm CH}_2 + {\rm FM}({\rm CH}_3 )_3 $$ \end{document}We suggest the occurrence of a radical exchange reaction for the Si, Sn, and Ge systems,\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm CF}_3 + {\rm M}({\rm CH}_3 )_4 \rightleftharpoons{\rm CF}_3 {\rm M}({\rm CH}_3 )_4 \to {\rm CH}_3 + {\rm CF}_3 {\rm M}({\rm C}{\rm H}_3 )_3 $$\end{document}with k exchange (CF 3 + Sn(Me) 4 ) ∼ 10 7 ml m −1 s −1 .