Question

Explain the fact that in aryl alkyl ethers (I)the alkoxy group activates the benzene ring towards electrophilic substitution and (ii) it directs the incoming substituents to ortho and para positions in the benzene ring.

Answer 1

Alkoxy group having +R effect donates electrons to benzene and thus, destabilizes it and high charge density exists at ortho and para positions. Now, solve the answer statement.

Complete answer:
Ethers are the organic compounds that have the general formula R–O–R′, where R and R′ represent the alkyl (it is a functional group which consists of only carbon and hydrogen atoms, which are arranged in a chain. E.g. Methyl group (-$\text{C}{{\text{H}} _ {3}}$) or aryl (the organic group which are derived from the aromatic (ring structures) by the removal of a hydrogen atom. E.g. phenyl group (-${{\text{C}} _ {6}} {{\text{H}} _ {5}}$) groups. It consists of a functional group i.e. the ether group in which the oxygen atom is connected to alkyl or aryl groups.
(i) The alkoxy group is a carbon and hydrogen group that are single bonded to oxygen i.e. R–O. in the electrophilic substitution reactions, electrophilic means electrophile (electron loving and have vacant orbitals to accept the electrons) and substitution means replacement. so, the electrophilic reactions are those chemical reactions in which a functional group is being replaced by the electrophile. The alkoxy group (R—O) having the +R effect (can donate electrons to the others) gives its electrons to the benzene ring and the electron density in the benzene ring increases and thus, destabilize the benzene ring and in turn the benzene ring gets activated for the electrophilic substitutions reactions in order to stabilize itself.

(ii) The alkoxy group directs the incoming group to the ortho and para positions due to the high charge electron density at ortho and para positions then, as compared to the meta position which has lesser charge density and acquires positive charge and hence, the incoming groups i.e. substituents are directed to the ortho and para positions.

Note:
Always keep in mind that the electron densities are always more at ortho and para positions and thus, mostly the substituents are directed to the orthotic-para positions than at the meta positions.