Chapter 10.6, Problem 2E

(a)

Interpretation Introduction

Interpretation: Structure of the major product expected from the ionic addition of $\text{HBr}$ to the substrate indicated should be written.

  

Concept introduction:Alkenes are considered electron-rich and undergo bromination addition reaction with ${\text{Br}}_2$ in presence of ${\text{CCl}}_{\text{4}}$ by electrophilic addition reaction.

The mechanism of ${\text{Br}}_2$ addition occurs in two steps. In the first step, nucleophilic olefin abstracts the electrophilic bromine atom from ${\text{Br}}_2$ and this result in attack of ${\text{Br}}^{+}$ 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 ${\text{Br}}^{-}$ attack from behind the electron-deficient carbon analogous to ${\text{S}}_{\text{N}}\text{2}$ attack.

(b)

Interpretation Introduction

Interpretation: Structure of the major product expected from the ionic addition of $\text{HBr}$ to the substrate indicated should be written.

  

Concept introduction:Alkenes are considered electron-rich and undergo bromination addition reaction with ${\text{Br}}_2$ in presence of ${\text{CCl}}_{\text{4}}$ by electrophilic addition reaction.

The mechanism of ${\text{Br}}_2$ addition occurs in two steps. In the first step, nucleophilic olefin abstracts the electrophilic bromine atom from ${\text{Br}}_2$ and this result in attack of ${\text{Br}}^{+}$ 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 ${\text{Br}}^{-}$ attack from behind the electron-deficient carbon analogous to ${\text{S}}_{\text{N}}\text{2}$ attack.

(c)

Interpretation Introduction

Interpretation: Structure of the major product expected from the ionic addition of ${\text{Br}}_2$ to the substrate indicated should be written.

  

Concept introduction:Alkenes are considered electron-rich and undergo bromination addition reaction with ${\text{Br}}_2$ in presence of ${\text{CCl}}_{\text{4}}$ by electrophilic addition reaction.

The mechanism of ${\text{Br}}_2$ addition occurs in two steps. In the first step, nucleophilic olefin abstracts the electrophilic bromine atom from ${\text{Br}}_2$ and this result in attack of ${\text{Br}}^{+}$ 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 ${\text{Br}}^{-}$ attack from behind the electron-deficient carbon analogous to ${\text{S}}_{\text{N}}\text{2}$ attack. For example, in cases of the trans-stilbene mechanistic pathway that occurs for addition bromine water is illustrated below.