Why will the reaction fail to work if the phase transfer catalyst is switched to ammonium chloride while retaining the same reactants, solvent, and base? Because it reacts with 2‑naphthol to make 2‑chloronaphthalene. Because it generates a powerful nitrogen‑based nucleophile in aqueous base. Because ammonium chloride is not soluble in dichloromethane solvent. Because ammonium chloride is not soluble in water.

Because ammonium chloride is not soluble in dichloromethane solvent.

Explanation:

It looks like you are trying to do a Williamson ether synthesis using 2-naphthol, allyl chloride, and a phase transfer catalyst like benzyltriphenylammonium chloride.

The phase transfer catalyst is soluble in dichloromethane and carries the alkoxide ions with it into the organic phase. This is where the reaction takes place.

If, instead, you use ammonium chloride, the reaction will fail.

NH₄Cl is a polar ionic solute. It is soluble in the polar aqueous phase but insoluble in the much less polar dichloromethane.

A is wrong. Naphthols do not undergo displacement reactions.

B is wrong. NH₄Cl generates the weak base NH₃ in aqueous NaOH.

D is wrong. Ammonium salts are soluble in water.