The bicyclic tertiary bromide shown does not react with ethanolic AgNO3 or with NaI in acetone, even on prolonged heating. What is the reason?

The bridgehead cannot flatten into a planar cation and its back side is shielded, so neither S_N1 nor S_N2 is feasible

It is a primary halide and primary halides never react

The bridgehead cannot flatten into a planar cation and its back side is shielded, so neither S_N1 nor S_N2 is feasible

Bromide is a poor leaving group at a tertiary centre

S_N2 is fast but the product reverts

JEE Main levelSingle correct optionDifficulty 2 of 3o3227

The bicyclic tertiary bromide shown does not react with ethanolic $AgNO X_{3}$ or with $NaI$ in acetone, even on prolonged heating. What is the reason?

AIt is a primary halide and primary halides never react
BThe bridgehead cannot flatten into a planar cation and its back side is shielded, so neither $S X_{N} 1$ nor $S X_{N} 2$ is feasible
CBromide is a poor leaving group at a tertiary centre
D $S X_{N} 2$ is fast but the product reverts

The compound is 1-bromobicyclo[2.2.1]heptane (1-bromonorbornane). The bridgehead carbon cannot become planar, so the cation needed for

S X_{N} 1

is highly strained; the cage also blocks backside attack, ruling out

S X_{N} 2

. It is inert to both pathways.