CIDNP —See Chemically induced

Carboxamides, formation from ArNj 243 2-Carboxybenzenediazonium zwitterion, see 2-Diazoniobenzenecarboxylate Carboxy-de-diazoniation 241 f. Carcinogenicity 319 Chemically induced dynamic nuclear polarization, see CIDNP Chloro-de-diazoniation 194, 230ff., 247, 270, 277... 

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. 

On the other hand, in accord with the free radical mechanism peroxynitrite is dissociated into free radicals, which are supposed to be genuine reactive species. Although free radical mechanism was proposed as early as in 1970 [111], for some time it was not considered to be a reliable one because a great confusion ensued during the next two decades because of misinterpretations of inconclusive experiments, sometimes stimulated by improper thermodynamic estimations [85]. The latest experimental data supported its reliability [107-109]. Among them, the formation of dityrosine in the reaction with tyrosine and 15N chemically induced dynamic nuclear polarization (CIDNP) in the NMR spectra of the products of peroxynitrite reactions are probably the most convincing evidences (see below). 

Such anomalous NMR spectra as observed in the above reactions have been called Chemically Induced Dynamic Nuclear Polarization (CIDNP) . CINDP should be due to nonequilibrium nuclear spin state population in reaction products. At first, the mechanism of CIDNP was tried to be explained by the electron-nuclear cross relaxation in free radicals in a similar way to the Overhauser effect [4b, 5b]. In 1969, however, the group of Closs and Trifunac [6] and that of Kaptain and Oosterhoff [7] showed independently that all published CIDNP spectra were successfully explained by the radical pair mechanism. CIDEP could also be explained by the radical pair mechanism as CIDNP. In this and next chapters, we will see how CIDNP and CIDEP can be explained by the radical pair mechanism, respectively. 

A new and little understood technique that is worthy of attention is chemically induced dynamic nuclear polarization (CIDNP). A hexane-ether solution containing w-butyl-lithium, n-butyl bromide and diphenylacetylene, gives a transient spectrum resembling that of but-l-ene in which some of the lines are inverted. The authors ascribe the phenomena to the presence of free-radical intermediates, although the lines show no evidence of broadening due to paramagnetic induced relaxation. See also ref. 7a. 

The role of nuclear spins in chemical reactions does not seem to have been noted before the advent of CIDNP. It is easy to see, however, how (i) and (ii) can lead to a sorting mechanism for nuclear spins and therefore to strong polarizations in radical pair products. This is demonstrated in Figure 1, which shows a typical photo-induced radical reaction. 

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