CIDNP Chemically Induced rearrangement

For a review of the application of CIDNP to rearrangement reactions, see Lepley, A.R. in Lepley Gloss Chemically Induced Magnetic Polarization, Wiley NY, 1973, p. 323. 

The ion pair spin multiplicity may be a valuable tool to affect the BET rates and to probe the ion pair dynamics via magnetic field effects [36], Even weak magnetic fields are known to influence relative probabilities of singlet and triplet reactions [34], Chemically induced dynamic nuclear polarization (CIDNP) is a particularly informative technique [12]. Many bond scission reactions and rearrangements in cyclic radical ions have been successfully explored using this approach. Both structural data (spin densities) and approximate kinetic informations are indirectly available from such experiments [12]. 

A search for an ionic Cope rearrangement has included (608). A concerted mechanism can only interchange (608) and (609), whereas (610) may intrude if ions (radicals) are involved. In fact, (610) is the product, and the absence of chemically induced dynamic nuclear polarization (CIDNP) effects together with trapping of the intermediate carbonium ion with borohydride as anethole support an ionic mechanism. ... 

Yang, L., Zhang, M., Liu, Y, Liu, Z., and Chow, Y.L., Triplex promoted intersystem crossing of ion-radical pairs in the photosensitized valence isomerization of quadricyclane chemically induced dynamic nuclear polarization (CIDNP) evidence,/. Chem. Soc., Chem. Commun., 1055-1056,1995. Kajitani, M., Fujita, X, Hisamatsu, N., Hatano, H., Akiyama, X, and Sugimori, A., Photochemical reactions of several adducts of metalladithiolenes and metalladithiazoles. Dissociation and rearrangement, Coord. Chem. Rev., 135, 175-180, 1994. 

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