The alkoxy group is ortho, para directing, and activates the aromatic ring in a manner similar to phenol. In the halogenation of anisole, the methoxy group activates the benzene ring, allowing bromination to occur even without an iron (III) bromide catalyst, yielding the para isomer in 90% yield.
How does the alkoxy group (-OR) influence the electrophilic substitution in phenylalkyl ethers, and what is the role of the methoxy group in the halogenation of anisole?
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The alkoxy group (-OR) in phenylalkyl ethers activates the benzene ring towards electrophilic substitution reactions. The methoxy group (OCH₃) in anisole, an example of a phenylalkyl ether, activates the benzene ring through resonance and electron donation. In halogenation reactions, the methoxy group enhances the electron density on the benzene ring, making it more susceptible to electrophilic attack. The role of the methoxy group is to facilitate the formation of the resonance-stabilized arenium ion intermediate, increasing the rate of halogenation. This activation effect contrasts with deactivating groups that decrease electron density and hinder electrophilic substitution.