Electron withdrawal inductive

Because of the increased importance of inductive electron withdrawal, nucleophilic attack on uncharged azole rings generally occurs under milder conditions than those required for analogous reactions with pyridines or pyridones. Azolium rings are very easily attacked by nucleophilic reagents reactions similar to those of pyridinium and pyrylium compounds are known azolium rings open particularly readily. 

The effects of fluonnation on carbanion stability are largely deduced from C-H acidity data (p. 988) [64], a-Halogens stabilize carbanions in the order Br > Cl > F, which IS opposite the inductive electron-withdrawing order and reflects the... 

The 10-fold disadvantage of the latter 1,2-H migration can be attributed to destabilization of the corresponding transition state by the inductively electron-withdrawing CF3 bystander.14... 

When bonded to an unsaturated carbon atom or to an arene, the fluorine atom exerts an inductive electron-withdrawing effect (cti>0) and an electron-donating effect through resonance (ctr < 0), both being very superior to the effects of the other halogens (Figure 1.1). The values of the Hammet parameters crj and fluorinated substituents are reported in Table 1.13. " ... 

A quantity called the radical stabilization energy (RSE) may be defined to relate the stabilities of substituted carbon radicals to the methyl radical. The effects of adjacent X , Z, and C substituents on the RSEs of carbon-centered radicals has been widely investigated [142,143]. The expectations based on simple orbital interaction theory as espoused above are widely supported by the experimental findings, except that when the the n donor or n acceptor ability of the group is weak and the inductive electron-withdrawing power is large, as in F3C and (Me N+CHj, the net effect is to destabilize the radical relative to the methyl radical [143]. The BDE of a C—H bond of a compound R—H is another measure of stability of the product radical, R. It is related to the RSE by... 

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