JEE Main 2022 · 28 Jun · Shift 1 · Chemistry Q73

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ChemistrySingle correct+4 / -1Question 73 of 90

The major product (P) in the reaction

$\mathrm{Ph{-}CH{=}CH{-}CH_2Br\xrightarrow{HBr}\ ?(P)}\qquad[\mathrm{Ph\ is\ {-}C_6H_5}]$

Reaction: cinnamyl bromide Ph-CH=CH-CH2Br treated with HBr gives product P.

PhCH(Br)CH(Br)CH

_2

PhCH

_2

CH(Br)CH

_2

PhCH(Br)CH

_2

_2

1,3-Dibromo-1-phenylpropane drawn as a zigzag: Ph-CH(Br)-CH2-CH2Br.

PhCH(Br)CH=CHBr

Answer and worked solution

Official answer: C

Markovnikov via the benzylic cation. $\mathrm{H^+}$ adds to the carbon next to $\mathrm{CH_2Br}$ , giving $\mathrm{Ph\overset{+}{C}H{-}CH_2{-}CH_2Br}$ , which takes $\mathrm{Br^-}$ : $\mathrm{PhCH(Br)CH_2CH_2Br}$ .

(C)

Topics:Alkenes Reactive intermediates

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JEE Main 2022 · 28 Jun · Shift 1, Chemistry question 73