Question

Phenyl methyl ether (anisole) reacts with HI to give phenol and methyl iodide and not iodobenzene and methyl alcohol because___________________.

• A. $I^{-}$ ion prefers to combine with the smaller group in order to minimise steric hindrance
• B. $I^{-}$ ion is not reactive towards benzene +
• C. phenol is formed as a result of hydrolysis of iodobenzene
• D. methyl alcohol formed during reaction reacts with $I^{-}$ to form methyl iodide.

Answer 1

Answer: (A)

$I^{-}$ ion prefers to combine with the smaller group in order to minimise steric hindrance

Phenyl methyl ether (anisole) $C{H}_{3}O{C}_6{H}_5$ reacts with HI to give phenol and methyl iodide and not iodobenzene and methyl alcohol because the lone pair of O are involved in resonace (+ mesomeric effect) with the benzene ring and imparts it a double bond character and increases the C-O bond strength with the benzene ring. Moreover, the reaction goes via $S_{N}2$ mechanism which prefers the attack of nucleophile $I^{-}$ from least hindered side of the molecule. Thus it prefers to attack the methyl group.

Hence Phenyl methyl ether (anisole) reacts with HI to give phenol and methyl iodide and not iodobenzene and methyl alcohol because $I^{-}$ ion prefers to combine with the smaller group in order to minimise steric hindrance.