Chapter 12, Problem 12.27E

Interpretation Introduction

(a)

Interpretation:

The structural formula for the alkene with molecular formula ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$ that gives $\text{2, 3-dibromopentane}$ as the product is to be stated.

Concept introduction:

The addition reactions are defined as the formation of one product by the combination of two or more products. For example, in halogenation, the addition of a halogen molecule results in the reduction of carbon-carbon double bond to carbon-carbon single bond and formation of haloalkane.

Answer to Problem 12.27E

The structural formula for the alkene with molecular formula ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$ that gives $\text{2, 3-dibromopentane}$ as product is ${\text{CH}}_3{\text{CH}}_2\text{CH}={\text{CHCH}}_3$.

Explanation of Solution

The reaction is shown below.

Figure 1

The product $\text{2, 3-dibromopentane}$ is prepared by the addition of bromine on $2$-pentene. The bromine molecule in non-polar solvent adds on the carbon-carbon double bond of $2$-pentene and reduces it to carbon-carbon single bond. The corresponding chemical reaction is shown below.

Figure 2

Conclusion

The structural formula for the alkene with molecular formula ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$ that gives $\text{2, 3-dibromopentane}$ as product is ${\text{CH}}_3{\text{CH}}_2\text{CH}={\text{CHCH}}_3$.

Interpretation Introduction

(b)

Interpretation:

The structural formula for the alkene with molecular formula ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$ that gives ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$ as the product is to be stated.

Concept introduction:

The addition reactions are defined as the formation of one product by the combination of two or more products. For example, in halogenation, the addition of a halogen molecule results in the reduction of carbon-carbon double bond to carbon-carbon single bond and formation of haloalkane.

Answer to Problem 12.27E

The structural formula for the alkene with molecular formula ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$ that gives pentane as the product is ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{CH}={\text{CHCH}}_{\text{3}}$ and ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_2\text{CH}={\text{CH}}_2$.

Explanation of Solution

The reaction is shown below.

${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}+{\text{H}}_2\stackrel{\text{Pt}}{\to }{\text{CH}}_3{\text{CH}}_2{\text{CH}}_2{\text{CH}}_2{\text{CH}}_3$

The product in the given reaction is pentane which can be prepared by the hydrogenation on the $1\text{-}$ pentene, and $\text{2-}$ pentene. The hydrogen molecule, in the presence of catalyst, adds on the carbon-carbon double bond of alkenes and reduces it to carbon-carbon single bond. The corresponding chemical reactions are shown below.

$\begin{array}{l}{\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{CH}={\text{CHCH}}_{\text{3}}+{\text{H}}_2\stackrel{\text{Pt}}{\to }{\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}\\ {\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_2\text{CH}={\text{CH}}_2+{\text{H}}_2\stackrel{\text{Pt}}{\to }{\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}\end{array}$

Conclusion

The structural formula for the alkene with molecular formula ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$ that gives pentane as the product is ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{CH}={\text{CHCH}}_{\text{3}}$ and ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_2\text{CH}={\text{CH}}_2$.

Interpretation Introduction

(c)

Interpretation:

The structural formula for the alkene with molecular formula ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$ that gives $\text{2-methylbutan-2-ol}$ as the product is to be stated.

Concept introduction:

The Markovnikov’s rule states that the addition of the $\text{H}-\text{X}$ to the alkene takes place in such a manner that the attachment of hydrogen atom takes place on the carbon atom having more number of hydrogen atoms.

Answer to Problem 12.27E

The structural formula for the alkene with molecular formula ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$ that gives $\text{2-methylbutan-2-ol}$ as product is shown below.

Explanation of Solution

The reaction is shown below.

Figure 2

The product in the reaction is $\text{2-methylbutan-2-ol}$ which can be prepared by the addition of ${\text{H}}_2\text{O}$ molecule on $\text{2-methylbut-2-ene}$ in the presence of ${\text{H}}_2{\text{SO}}_4$ by Markovnikov’s rule. The hydroxide ion will attach to the more substituted carbon. The corresponding chemical reaction is shown below.

Figure 3

Conclusion

The structural formula for the alkene with molecular formula ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$ that gives $\text{2-methylbutan-2-ol}$ as product is shown in Figure 3.

Interpretation Introduction

(d)

Interpretation:

The structural formula for the alkene with molecular formula ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$ that gives $\text{2-bromopentane}$ as product is to be stated.

Concept introduction:

The Markovnikov’s rule states that the addition of the $\text{H}-\text{X}$ to the alkene takes place in such a manner that the attachment of hydrogen atom takes place on the carbon atom having more number of hydrogen atoms.

Answer to Problem 12.27E

The structural formula for the alkene with molecular formula ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$ that gives $\text{2-bromopentane}$ as product is ${\text{CH}}_2={\text{CHCH}}_2{\text{CH}}_2{\text{CH}}_{\text{3}}$.

Explanation of Solution

The given reaction is shown below.

Figure 4

The product in the given reaction is $\text{2-bromopentane}$ which can be prepared by the addition of $\text{HBr}$ molecule on $\text{1-pentene}$ by Markovnikov’s rule. The bromide ion will attach to the more substituted carbon. The corresponding chemical reaction is shown below.

Figure 5

Conclusion

The structural formula for the alkene with molecular formula ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$ that gives $\text{2-bromopentane}$ as product is ${\text{CH}}_2={\text{CHCH}}_2{\text{CH}}_2{\text{CH}}_{\text{3}}$.