Gas Phase Reactivities of Isomeric Ions: Methylenediphenylcyclopropane and Diphenylmethylenecyclopropane.

Gas phase ion/molecule reactions have been used to probe the structure of ions obtained by electron impact upon 1-(diphenylmethylene)cycl opropane and 2,2-diphenyl-1-methylenecyclopropane. The resulting ions of molecular composition C sub (16) H sub (14) (m/z 206 sup + ) were reacted with charge transfer reagents (7.1 IP 8.8eV), giving evidence for the presence of isomeric ions with different reactivities. The less reactive ion is identified as a trimethylenemethane species (TMM sup + ) in which one cyclopropane bond is broken; the more reactive ions are assigned as vertical ions, in which the cyclopropane ring is unaffected. The vertical ions have recombination energies of 8.44+- 0.05eV, whereas TMM sup + has one of 7.41+-0.05eV.