Here, 4-methoxybenzaldehyde in series of reaction finally forms 4-(iodomethyl) phenol
(A). Let us compute the reaction step by step with mechanism as follows
(i) In first step, oxidising agent (
p-methoxybenzaldehyde) reacts with formaldehyde in presence of strong base
NaOH to give
p-methoxybenzyl alcohol along with sodium salt of methanoic acid. It is known as Cannizzaro's reaction.
(ii) In second step, deprotonation of
p-methoxybenzyl alcohol in presence of sodium hydride
(NaH) to form alkoxide which further react with bromoethane in presence of DMF to give 1-ethoxymethyl-4-methoxybenzene.
(iii) In last step, 1-ethoxymethyl-4-methoxybenzene undergoes solvolysis reaction followed by
SN2 attack of two iodide ion (I
−) to give 4-iodomethyl phenol, iodoform and iodoethane.