Chapter 6, Problem 77P

(a)

Interpretation Introduction

Interpretation:

The products obtained from the reaction of $\text{1-ethylcyclohexene}$ with the given reagents should be determined.

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:

(b)

Interpretation Introduction

Interpretation:

The products obtained from the reaction of $\text{1-ethylcyclohexene}$ with the given reagents should be determined.

Concept Introduction:

$H_2$addition:

Catalytic hydrogenation in presence of $\text{Pd/C}$ is an example for syn addition of hydrogen.

For cyclic reactants, the addition of $H_2$ will form cis enantiomers since two hydrogens adds to one side of the double bond.

(c)

Interpretation Introduction

Interpretation:

The products obtained from the reaction of $\text{1-ethylcyclohexene}$ with the given reagents should be determined

Concept Introduction:

Hydroboration oxidation:

• Used to convert an alkene to alcohol.
• Reagent used is ${\text{BH}}_{\text{3}}\text{or}{\text{R}}_{\text{2}}\text{BH}$
• Boron is the electrophile which accepts electrons from the alkene and forms bond with one ${\text{sp}}^{\text{2}}$ carbon and give ${\text{H}}^{\text{-}}$ to other ${\text{sp}}^{\text{2}}$ carbon.
• After the addition reaction, an aqueous solution of $\text{NaOH}\text{and}{\text{H}}_{\text{2}}{\text{O}}_{\text{2}}$ is added and $\text{OH}$ will be in boron’s place.

(d)

Interpretation Introduction

Interpretation:

The products obtained from the reaction of $\text{1-ethylcyclohexene}$ with the given reagents should be determined

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.