Perfluoroalkyl group, inductive effect

Under sonication conditions, the reaction of perfluoroalkyl bromides or iodides with zinc can be used to effect a variety of functionalization reactions [39, 40, 41, 42] (equation 30) Interestingly, the ultrasound promoted asymmetric induction with the perfluoroalkyl group on the asymmetric carbon was achieved by the reaction of perfluoroalkyl halides with optically active enamines in the presence of zinc powder and a catalytic amount of dichlorobisftc-cyclopenta-dienyl)titanium [42] (equation 31)... 

Fluorination has a particularly profound effect on the additions of nucleophiles to per-fluorinated alkenes where the intermediate is anionic. Such processes are dramatically assisted by the strongly stabilizing influence of perfluoroalkyl groups substituted at the incipient anionic site.66 Similar to carbocations (see Section 1.4.), the effect of fluorination in such systems is often ambiguous when monofluorination is involved. a-Halogens generally stabilize anions in the order bromine > chlorine > fluorine, which is the exact opposite to the inductive electron-withdrawing order of the substituents. This effect reflects the importance of l7t-repulsion.67... 

Perfluoroalkyl iodides do not act as alkylating agents as the nonfluori-nated iodides do. The strong inductive effect of the perfluoroalkyl group... 

It is generally recognised that the inductive effect should be subdivided into a polarisation effect on the o-bond framework and also on the rr-electrons, and it has been indicated that a major effect of strongly electron-withdrawing groups like perfluoroalkyl is by a through-space polarisation of the aromatic rr-electrons (direct field effect). 

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