Isomerization of unsaturated radicals. V. Unimolecular isomerization of hot α,α‐ and α,β‐dimethallyl radicals

The 147 nm photolysis of 3,3 dimethylbut‐1‐ene leads mainly to the formation of very hot (≅375 kJ/mol) α,α‐dimethallyl radicals. On the other hand, that of 3‐methyl‐ cis ‐and trans ‐pentene‐2, as well as that of 2,3‐dimethylbut‐1‐ene is a source of very hot α,β‐dimethallyl radicals. These allylic radicals are coolled down using pressure and are allowed to combine with available methyl radicals. From the formation of various C 6 H 12 products, it is concluded that the very hot α,α‐ radical isomerizes towards the α,β‐structure at low pressures and vice versa . The equilibrium constant of the following process has been evaluated to be 1.72 ± 0.30.\documentclass{article}\pagestyle{empty}\begin{document}$${\rm CH}_3{\rm C}({\rm CH}_3){\rm CHCH}_2 ^ * \Leftrightarrow {\rm CH}_2 {\rm C}({\rm CH}_{\rm 3}){\rm CHCH}_3 ^ *$$\end{document}