Cyclopropane derivatives radiolysis

Radical cations of the same general structure type as those derived from cis- and tratw-diphenylcyclopropane have been established for numerous cyclopropane derivatives, including the parent, 1,2-di-, 1,1,2-tri- and 1,1,2,2-tetramethylcyclo-propane (Table 3). Two of these systems provide a direct comparison between the results of CIDNP and ESR experiments. In both cases, the ESR spectra observed by Williams and coworkers following pulse radiolysis in frozen solutions [293, 296, 297] show splitting patterns supporting the presence of spin density on two carbon centers, thus confirming the structure type (102) assigned on the basis of CIDNP results. 

Exposure of several methyl-substituted derivatives to y-radiolysis at 77 K in cryogenic matrices gave rise to a family of radical cations of the same structure type, some of which had been previously identified on the basis of CIDNP results. We begin with a discussion of the CIDNP investigations, since they preceded the ESR studies of all species but the prototype. The first CIDNP results attributed to a cyclopropane radical cation were observed during the photoreaction between 1,4-dicyanonaphthalene and cis-l,2-diphenylcyclopropane. However, the nature of the cyclopropane radical cation was characterized by CIDNP effects observed during the reaction of chloranil with cis- and /rans-l,2-diphenylcyclo-propane. ... 

Among the simple cycloalkanes, we first discuss electron transfer from the three-to eight-membered cycloalkane prototypes to electron holes generated by radiolysis in different matrices, giving rise to the simple cycloalkane radical cations. Because of the significant interest they have attracted, the electron-transfer reactions of cyclopropane and, to a lesser extent, cyclobutane derivatives will be treated separately. Finally, electron transfer from some bicyclic hydrocarbons and the resulting radical cations will be discussed in a separate section (Section 2.4). 

As mentioned earlier, the cyclopropane radical cation, prepared by y-radiolysis in rigid matrices, had an ESR spectrum compatible with the trimethylene structure Ai) [78, 79]. Irradiation of several methyl-substituted derivatives at 77 K gave rise... 

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