Nucleophilic constant orbital

The EPR spectra of electrolytically produced anion radicals of Q -aminoanthraquin-ones were measured in DME and DMSO. The isotropic hyperfine coupling constants were assigned by comparison with the EPS spectra of dihydroxy-substituted antraquinones and molecular-orbital calculations. Isomerically pure phenylcarbene anion (PhCH ) has been generated in the gas phase by dissociative electron ionization of phenyldiazirine. PhCH has strong base and nucleophilic character. It abstracts an S atom from and OCS, an N atom from N2O, and an H atom from... 

The e j rate constants correlate better with normal o- values derived from electrophilic substitution than with a para values obtained from data of nucleophilic reactions. This is not surprising in view of the fact that the e]fq reactions constitute an interaction of an electron with the 77-orbitals of the ring, as in electrophilic substitution, rather than with effects on electron distribution and polarizability of a certain substituent. 

When considering the rate constants for deprotonation reported in Table 2 one should, however, take into account that in methylbenzene radical cations with < 3 methyl groups, nucleophilic attack of water on the aromatic ring can compete efficiently with side-chain deprotonation. An elegant explanation which accounts for this competition has been provided for the toluene radical cation on the basis of the three-electron three-orbital three-configuration approach [135, 136]. Three electrons are involved in the deprotonation reaction—the unpaired electron delocalized over... 

Consequently, reaction (3) should depend on the stability of the cation corresponding to the radical R. This is clearly the case, as shown in Scheme 8 by the good correlation obtained between the stability of the cation (measured by the SN1 rate constant) and k0 [21]. This interpretation explains why radicals having a a configuration (pyramidalized radicals) such as the cyclopropyl or the bicyclo[2.2.1]heptyl-l [34], less nucleophilic than n radicals (quasi planar radicals having their unpaired electron in a p orbital), give no or only small quantities of... 

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