Radicals perchlorobenzyl

The reactivity of free radicals is linked to their stability. Reactivity is a function of spin density of the atom and the type of orbital occupied by the unpaired electrons. Increasing the number of atoms in a radical generally decreases reactivity, making monoatomic radicals such as Li and F very reactive. Conjugation decreases the spin density and therefore the reactivity. The resultant delocalization does not necessarily, however, lead to a very stable radical. Steric effects play a significant role in radical reactivity. "If the bulkiness of the surrounding substituents exceeds 12-fold that of the central atom containing a radical site", the radical is unreactive and fails to react at all in many cases. Triphenylsilyl radical (45), for example, is very reactive but perchlorobenzyl radical (46) is not. 

Thermal dimerization of 2,3,5,6-tetrachloro-p-phenylenediimine 351 A remarkable benzidine rearrangement 352 Condensation of aromatic perchloroamines 353 Perchlorinated organic radicals and related intermediates 354 Perchlorobenzyl radicals 354 Perchlorodiphenylmethyl radicals 355 Perchlorotriphenylmethyi radicals 361 Perchloro-9-phenylfluorenyl radicals and related species 384 Inert perchloro-aza-radicals 389 Perchloro-p-quinodimethanes, perchloro-/ -xylylenes and related compounds 390... 

Fig. 10 All-planar scale model of perchlorobenzyl radical (PB-), showing the steric interactions among a-and o-chlorines.

Fig. 39 Esr spectrum of the perchlorobenzyl radical (PB-), consisting of seven lines 2nl + 1 lines / = 3/2, n = 2) due to hyperfine coupling with the two a-chlorines.

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