Number of moles of AgCl formed in the following reaction is _____________

Solution

Chemistry ma’am · 3 steps

Silver nitrate only pulls off a chloride that can leave as a stable carbocation, so check each C–Cl bond.

1. How AgNO3 works. Ag⁺ grabs the chlorine and AgCl precipitates. That happens readily only when the C–Cl bond breaks easily and leaves a stable carbocation behind (an S_N1-type ionisation).

   Chlorine	Type of carbon	Gives AgCl?
   On the benzene ring	aryl, C–Cl has partial double-bond character	no
   On -CH=CHCl	vinyl, C–Cl has partial double-bond character	no
   On Ar-CH(Cl)⁻	secondary benzylic, cation stabilised by the ring	yes
   On -C(CH₃)₂Cl	tertiary, cation stabilised by three alkyl groups	yes

2. Aryl and vinyl. In aryl and vinyl chlorides, a lone pair on Cl is delocalised into the π system, which strengthens the C–Cl bond. The phenyl and vinyl cations that would form are also very unstable, so no precipitate forms.
3. So. Only the benzylic and tertiary chlorines are removed, so one mole of the compound gives X = 2 moles of AgCl.

The common slip: 4. Counting every chlorine in the structure gives 4, but the aryl and vinyl chlorines do not ionise and stay bonded.

The idea to keep. With AgNO₃, think carbocation stability: benzylic, allylic and tertiary halides precipitate AgCl readily, while aryl and vinyl halides do not react.

Answer from the NTA final answer key. Solution by PrepWiser.