Inductive effects of halogens

A very similar situation is encountered in the electrophilic addition of unsymmetrical adducts (e.g. HBr) to vinyl halides (e.g. CH2=CHBr), where the inductive effect of halogen controls the rate, but relative mesomeric stabilisation of the carbocationic intermediate controls the orientation, of addition (p. 185). 

Inductive effect of halogen attracts electrons from ring... 

The inductive effect of halogens. The halogens are more electronegative than carbon and have an electron-withdravdng inductive effect. Aryl halides, therefore, react more slowly in electrophilic aromatic substitution than benzene does. 

Each of these intermediates can be hthiated in the 2-position in good yield. The reactivity toward hthiation is due to the inductive effect of the nitrogen atom and coordination by oxygen from the N-substituent. A wide variety of electrophiles can then carry out substitution at the 2-position. Lithiation at other positions on the ring can be achieved by halogen—metal exchange 3-hthio and 5-hthioindoles have also been used as reactive intermediates. 

Because inductive effects operate through cr bonds and are dependent on distance, the effect of halogen substitution decreases as the substituent moves farther from the carboxyl. Thus, 2-chlorobutanoic acid has p/chlorobutanoic acid has p/chlorobutanoic acid has p/C., = 4.52, similar to that of butanoic acid itself. 

Haloalkane,. see Alkyl halide Haloform reaction, 854-855 Halogen, inductive effect of, 562 resonance effect of, 563 Halogenation, aldehydes and, 846-848... 

The applicability of these methods is restricted to polyhalogenated compounds, since the inductive effect of the halogen atoms is necessary for facilitating formation of the carbanion. 

If the competition data are compared with electronegativity values for the halogens 85>, then tetrafluorobenzyne is clearly in an anomalous position. The only reasonable explanation available at present is that tetrafluorobenzyne is so destabilized by the inductive effect of the fluorine atoms that it has lost a considerable amount of the selectivity which arynes normally show. Estimates for the heats of formation of the isomeric dichlorobenzynes and for tetrachlorobenzyne have recently been made from mass spectrometric studies and these do indicate a low stability for tetrachlorobenzyne 86>. Evidently more data are required for the tetrahalogenobenzynes. 

CX3 is a good leaving group because of the electron-withdrawing inductive effect of the three halogen atoms this activates the carbonyl carbon atom in (100) to nucleophilic attack, and also stabilises the... 

In contrast, in basic solution halogenation tends to proceed to polyhalogenated products. This is because the inductive effect of a halogen accelerates base-catalyzed... 

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