Kinetic applications of electron paramagnetic resonance spectroscopy. XXIII. Cyanomethyl radicals

Dicyanomethyl and tricyanomethyl have been prepared and examined by EPR spectroscopy. Their EPR parameters at 20\ub0 are: H\u10a(CN)2, g = 2.0033, aH = 19.18, aN = 2.75, a13C\u3b1 = 29.18 G; \u10a(CN)3, g = 2.0033, aN = 2.28, a13C\u3b1 = 22.06, a13C\u3b2 = 18.20. It is concluded, on the basis of the 13C\u3b1 couplings and from the results of INDO calculations, that both radicals are planar. The 13C\u3b1 couplings, which were measured with enriched material, increase slightly with increasing temperature because the magnitude of the out-of-plane vibrations of the C\u3b1 substituents increases. Both radicals decay with second-order kinetics, the H\u10a(CN)2 radical at close to the diffusion-controlled limit (k2EPR = 1.2 7 1.2 7 109 sec-1 at 20\ub0), but \u10a(CN)3 decays considerably more slowly.Peer reviewed: YesNRC publication: Ye

Kinetic applications of electron paramagnetic resonance spectroscopy. 28. N-alkoxy-N-alkylamino, N-alkoxyamino, and N-alkoxyanilino radicals

Radicals of the types mentioned in the title have been generated and the kinetics and products of their decay have been examined. N-Alkoxy-N-alkylamino, RO\u1e44R\u2032, and N-alkoxyamino, RO\u1e44H, radicals decay with second-order kinetics at about 10% of the diffusion-controlled rate. N-Alkoxyanilino radicals, RO\u1e44C6H5, are much more persistent, they decay with first-order kinetics and exist in equilibrium with their dimers, \u394H 3c 13.5 kcal/mol. N-Alkoxyaminos yield alcohols as the only organic products of decay, and N-ethoxyanilino yields only ethanol and trans-azobenzene. N-Alkoxy-N-alkylamino radicals generally yielded complex mixtures of products. However, N-benzyloxy-N-benzylamino gave approximately equimolar amounts of O-benzylbenzaldoxime, benzyl alcohol, benzaldehyde, and \u3c9,\u3c9\u2032-azotoluene. The first of these products must arise by disproportionate. It is proposed that the other three products are formed via a Russell-type six-center concerted decomposition of an N-N coupled product. This type of decay appears to be confined to N-benzyloxy-N-alkylamino radicals, presumably because the benzylic hydrogens are activated by the adjacent phenyl group.Peer reviewed: YesNRC publication: Ye

Some unusually long-lived \u3b1-aminoalkyl radicals [18]

Peer reviewed: YesNRC publication: Ye

Kinetic applications of electron paramagnetic resonance spectroscopy. XXI. Some mono-, di-, and trialkylhydrazyls

The kinetics, mechanism, and products of decay of some mono-, 1,2-di-, and trialkylhydrazyls have been examined. 1-Alkylhydrazyls decay with second-order kinetics at the diffusion-controlled limit, 1,2-Diisopropylhydrazyl undergoes a very rapid second-order decay, which is a \u3b2-disportionation to hydrazine and azo compound. According to their structure, trialkylhydrazyls may decay by a fast second-order \u3b2-disproportionation (alkyl-H \u2192 N) or by a slow ,\u3b2-scission (loss of alkyl and formation of an azo compound). These results, together with previously reported data on 2,2-diaikylhydrazyis, are discussed in relation to the possibilities of isolating persistent alkyl hydrazyl radicals.Peer reviewed: YesNRC publication: Ye