The formation of both meso-stilbene dibromide and dl-stilbene dibromide should be demonstrated with the help of carbocation intermediate formed upon addition of bromine to ( E ) -stilbene . Concept introduction: Alkenes are considered electron-rich and undergo bromination addition reaction with Br 2 in presence of CCl 4 by electrophilic addition reaction. The mechanism of Br 2 addition occurs in two steps. In the first step, nucleophilic olefin abstracts the electrophilic bromine atom from Br 2 and this result in attack of Br + on the electron-rich olefinic bond that forms a sigma bond to each end of the olefinic bond. Such interaction leads to a three-membered bromonium ion intermediate. In the second step, the strained bromonium ion intermediate opens while Br − attack from behind the electron-deficient carbon analogous to S N 2 attack.

Question

TReferences] Indicate, by letter(s), the position(s) on the ring at which substitution occurs when the aromatic compounds shown undergo bromination with Br, FeBr3 (when necessary). .H CN HO

Answer 1

Question

Chapter 10.6, Problem 16E

Interpretation Introduction

Interpretation:The formation of both meso-stilbene dibromide and dl-stilbene dibromide should be demonstrated with the help of carbocation intermediate formed upon addition of bromine to (E)-stilbene .

Concept introduction:Alkenes are considered electron-rich and undergo bromination addition reaction with Br2 in presence of CCl4 by electrophilic addition reaction.

The mechanism of Br2 addition occurs in two steps. In the first step, nucleophilic olefin abstracts the electrophilic bromine atom from Br2 and this result in attack of Br+ on the electron-rich olefinic bond that forms a sigma bond to each end of the olefinic bond. Such interaction leads to a three-membered bromonium ion intermediate.

In the second step, the strained bromonium ion intermediate opens while Br− attack from behind the electron-deficient carbon analogous to SN2 attack.

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TReferences] Indicate, by letter(s), the position(s) on the ring at which substitution occurs when the aromatic compounds shown undergo bromination with Br, FeBr3 (when necessary). .H CN HO

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