[figure] In the above reaction product 'P' is
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Answer
(1) [figure]
Solution
The phenyl ring on the neighbouring carbon takes part in the reaction (neighbouring group participation, NGP). Its π electrons push out Br- from the back side and a bridged phenonium ion is formed. CN- then opens the three-membered ring at the carbon carrying –OCH3, because this carbon holds the positive charge better (lone pair of O), and the ring becomes aromatic again:
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So the phenyl group stays on its own carbon and CN simply takes the place of Br; the carbon skeleton does not change.
∴ P = C6H5CH(CH3)CH(OCH3)CN, which is structure (1).
(2), (3) and (4) need a phenyl, methyl or –OCH3 shift, which does not take place here, so they are wrong.
Answer: (1)