Halogenation electronic effects

Inductive effects (Section 16.4) are also important in determining alcohol acidities. Electron-withdrawing halogen substituents, for example, stabilize an alkoxide ion by spreading out the charge over a larger volume, thus making the alcohol more acidic. Compare, for example, the acidities of ethanol (p/tcrt-butyl alcohol (p/

Equipped with these reference trends for steric and electronic effects, one is prepared to survey more general classes of electrophilic aromatic substitution on benzocycloalkenes. Such reactions include nitration, halogenation, sulfonation, and alkylation. Each has its own mechanistic peculiarities, but their product distributions can be rationalized by consideration of the appropriate reference. 

Electronic effects that modify the polarity of a bond have an influence on chemical shifts. If the position of a methyl group in an alkyl halide CH3-X is compared to that of methane, the shift in signal increases with the electronegativity of the halogen atom (Table 9.3). 

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