Chapter 6, Problem 78P

(a)

Interpretation Introduction

Interpretation:

The products of the following reactions should be determined and if the products can exist as stereoisomers, it must be shown.

Concept Introduction:

Halogen addition to an alkene:

The addition reaction of halides to alkenes leads to the formation of vicinal dihalide as the product. The two halogens will be on the adjacent carbons.

Mainly ${\text{Br}}_{\text{2}}\text{and}{\text{Cl}}_{\text{2}}$ undergo addition reaction with alkenes and the reaction is carried out in an inert solvent such as dichloromethane.

In general, the reaction can be shown as below.

When the bromine approaches the alkene, one bromine accepts the electrons from alkene and give them to the other bromine and a cyclic bromonium ion intermediate is formed.

The formed unstable intermediate reacts with ${\text{Br}}^{\text{-}}$ and the product is formed.

(b)

Interpretation Introduction

Interpretation:

The products of the following reactions should be determined and if the products can exist as stereoisomers, it must be shown.

Concept Introduction:

Acid Catalysed addition of water: When water is added to alkene in the presence of an acid, the product formed will be an alcohol.

The electrophile ${\text{H}}^{\text{+}}$ adds to the nucleophile alkene and a carbocation is formed. Then water adds to the carbocation and form a protonated alcohol and in the last step it loses a proton and final an alcohol is formed.

(c)

Interpretation Introduction

Interpretation:

The products of the following reactions should be determined and if the products can exist as stereoisomers, it must be shown.

Concept Introduction:

Halogen addition to an alkene:

The addition reaction of halides to alkenes leads to the formation of vicinal dihalide as the product. The two halogens will be on the adjacent carbons.

Mainly ${\text{Br}}_{\text{2}}\text{and}{\text{Cl}}_{\text{2}}$ undergo addition reaction with alkenes and the reaction is carried out in an inert solvent such as dichloromethane.

In general, the reaction can be shown as below.

When the bromine approaches the alkene, one bromine accepts the electrons from alkene and give them to the other bromine and a cyclic bromonium ion intermediate is formed.

The formed unstable intermediate reacts with ${\text{Br}}^{\text{-}}$ and the product is formed.

(d)

Interpretation Introduction

Interpretation:

The products of the following reactions should be determined and if the products can exist as stereoisomers, it must be shown.

Concept Introduction:

Addition of a hydrogen halide to an alkene:

An alkyl halide is formed, if an hydrogen halide is used as an electrophile in the addition to alkene.

The ${\text{H}}^{\text{+}}$ adds to one of the ${\text{sp}}^{\text{2}}$ carbon and the nucleophile halide ion to other ${\text{sp}}^{\text{2}}$ carbon

The general reaction is represented as: