Which one is most reactive towards `S_(N^(1))` reaction?

Options

A. `C_(6)H_(5)CH(CH_(3))Br`
B. `C_(6)H_(5)(CH_(3))(C_(6)H_(5))Br`
C. `C_(6)H_(5)CH_(2)Br`
D. `C_(6)H_(5)CH(C_(6)H_(5))Br`

Answer

B

Explanation

`S_(N^(1))` reaction involves the formation of carbocation intermediated. More stable is the carbocation intermediate, more reactive will be the alkyl/aryl halides towards `S_(N^(1))` reaction
`C_(6)H_(5)C(CH_(3))(C_(6)H_(5))Br` is most reactive towards `S_(N^(1))` reaction.
`C_(6)H_(5)C^(+)(CH_(3))(C_(6)H_(5))gt (C_(6)H_(5))C^(+)H(C_(6)H_(5))gt(C_(6)H_(5))CH^(+(CH_(3))gt C_(6)H_(5)overset(**)(C )H_(2)`.