Chapter 6, Problem 6.15P

(a)

Interpretation Introduction

Interpretation:

The structure for isomeric carbocation intermediate formed on treatment of given alkene in presence of given acid has to be drawn, labelled and identified that whether the isomeric carbocation forms readily or not.

Concept Introduction:

Leaving group: it is the fragment that leaves the substrate in a chemical reaction with a pair of electrons.

Nucleophile: donates pair of electrons to positively charged substrate resulting in the formation of chemical bond.

Carbocation: carbon ion that bears a positive charge on it.

Carbocation stability order:

Resonance stabilization: Due to the delocalization of electrons within the molecule the overall energy becomes lower and makes that molecule more stable.

Explanation of Solution

1. 1. There are two possibilities present in attack of proton from acid to the given alkene.
2. 2. First is ${\text{H}}^{\text{+}}$ from $\text{HCl}$ attacks the carbon with one hydrogen (secondary carbon) in $\text{C=C}$ and results to form tertiary carbocation.
3. 3. Second is ${\text{H}}^{\text{+}}$ from $\text{HCl}$ attacks the carbon with 0 hydrogen (tertiary carbon) in $\text{C=C}$ and results to form secondary carbocation.
4. 4. Of these the tertiary carbocation forms readily since it is more stable than the secondary carbocation.

(b)

Interpretation Introduction

Interpretation:

The structure for isomeric carbocation intermediate formed on treatment of given alkene in presence of given acid has to be drawn, labelled and identified that whether the isomeric carbocation forms readily or not.

Concept Introduction:

Leaving group: it is the fragment that leaves the substrate in a chemical reaction with a pair of electrons.

Nucleophile: donates pair of electrons to positively charged substrate resulting in the formation of chemical bond.

Carbocation: carbon ion that bears a positive charge on it.

Carbocation stability order:

Resonance stabilization: Due to the delocalization of electrons within the molecule the overall energy becomes lower and makes that molecule more stable.

Explanation of Solution

1. 1. There are two possibilities present in attack of proton from acid to the given alkene.
2. 2. First is ${\text{H}}^{\text{+}}$ from $\text{HCl}$ attacks the carbon with one hydrogen and one methyl group (secondary carbon) in $\text{C=C}$ and results to form secondary carbocation.
3. 3. Second is ${\text{H}}^{\text{+}}$ from $\text{HCl}$ attacks the carbon with 1 hydrogen and one ethyl group (secondary carbon) in $\text{C=C}$ and results to form another secondary carbocation.
4. 4. Both carbocations formed are secondary hence both have equal rates.

(c)

Interpretation Introduction

Interpretation:

The structure for isomeric carbocation intermediate formed on treatment of given alkene in presence of given acid has to be drawn, labelled and identified that whether the isomeric carbocation forms readily or not.

Concept Introduction:

Leaving group: it is the fragment that leaves the substrate in a chemical reaction with a pair of electrons.

Nucleophile: donates pair of electrons to positively charged substrate resulting in the formation of chemical bond.

Carbocation: carbon ion that bears a positive charge on it.

Carbocation stability order:

Resonance stabilization: Due to the delocalization of electrons within the molecule the overall energy becomes lower and makes that molecule more stable.

Explanation of Solution

1. 1. There are two possibilities present in attack of proton from acid to the given alkene.
2. 2. First is ${\text{H}}^{\text{+}}$ from $\text{HCl}$ attacks the carbon that does not have methyl bonded with it (secondary carbon) in $\text{C=C}$ and results to form tertiary carbocation.
3. 3. Second is ${\text{H}}^{\text{+}}$ from $\text{HCl}$ attacks the carbon with methyl substitution (tertiary carbon) in $\text{C=C}$ and results to form secondary carbocation.
4. 4. Of these the tertiary carbocation forms readily since it is more stable than the secondary carbocation.

(d)

Interpretation Introduction

Interpretation:

The structure for isomeric carbocation intermediate formed on treatment of given alkene in presence of given acid has to be drawn, labelled and identified that whether the isomeric carbocation forms readily or not.

Concept Introduction:

Leaving group: it is the fragment that leaves the substrate in a chemical reaction with a pair of electrons.

Nucleophile: donates pair of electrons to positively charged substrate resulting in the formation of chemical bond.

Carbocation: carbon ion that bears a positive charge on it.

Carbocation stability order:

Resonance stabilization: Due to the delocalization of electrons within the molecule the overall energy becomes lower and makes that molecule more stable.

Explanation of Solution

1. 1. There are two possibilities present in attack of proton from acid to the given alkene.
2. 2. First is ${\text{H}}^{\text{+}}$ from $\text{HCl}$ attacks the carbon that has 0 hydrogens with it (tertiary carbon) in $\text{C=C}$ and results to form primary carbocation.
3. 3. Second is ${\text{H}}^{\text{+}}$ from $\text{HCl}$ attacks the carbon with 2 hydrogens (primary carbon) in $\text{C=C}$ and results to form tertiary carbocation.
4. 4. Of these the tertiary carbocation forms readily since it is more stable than the primary carbocation.