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Which of the following will NOT undergo $S_N1$ reaction with $OH^-$?
A
- 
B
$CH_2=CH-CH_2Cl$ (allyl chloride)
C
$(CH_3)_3CCl$ (tert-butyl chloride)
D
- 
Detailed Solution
$S_N1$ reactions proceed via a carbocation intermediate and are favoured when the carbocation is stabilised. Benzyl chloride (resonance-stabilised benzylic cation), allyl chloride (resonance-stabilised allylic cation), and tert-butyl chloride (stable tertiary carbocation) all readily undergo $S_N1$. 2-Phenylethyl chloride would form an unstabilised primary carbocation (the phenyl ring is not directly attached to the carbon bearing the leaving group), so it does not readily undergo $S_N1$.