Chapter 12, Problem 12.18E

Interpretation Introduction

(a)

Interpretation:

Whether the alkene $\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{CH}={\text{CH}}_{\text{2}}\right)$ could exist as cis-trans isomers or not is to be predicted. The structural formulas and names of both the cis- and the trans- isomers are to be stated if the corresponding alkene shows isomerism.

Concept introduction:

Those compounds which have the same molecular formula but have different arrangements of atoms are known as isomers. The phenomenon is called isomerism. The isomers are generally classified as structural isomers and stereoisomers. Stereoisomers are further divided into two categories diastereomers and enantiomers.

Answer to Problem 12.18E

The alkene $\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{CH}={\text{CH}}_{\text{2}}\right)$ will not have cis-trans isomers.

Explanation of Solution

The alkene is ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{CH}={\text{CH}}_{\text{2}}$.

A compound shows cis-trans isomerism when the substituent groups on the carbon atoms that are connected via double bond are different. The alkene has the same substituted groups on a carbon atom that is on the right-hand side of the double bond. Therefore; it will not have cis-trans isomerism.

Conclusion

The alkene $\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{CH}={\text{CH}}_{\text{2}}\right)$ will not have cis-trans isomers.

Interpretation Introduction

(b)

Interpretation:

Whether the alkene $\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{CH}={\text{CHCH}}_{\text{2}}{\text{CH}}_{\text{3}}\right)$ could exist as cis-trans isomers or not is to be predicted. The structural formulas and names of both the cis- and the trans- isomers are to be stated if the corresponding alkene shows isomerism.

Concept introduction:

Those compounds which have the same molecular formula but have different arrangements of atoms are known as isomers. This phenomenon is called isomerism. The isomers are generally classified as structural isomers and stereoisomers. Stereoisomers are further divided into two categories diastereomers and enantiomers.

Answer to Problem 12.18E

The alkene $\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{CH}={\text{CHCH}}_{\text{2}}{\text{CH}}_{\text{3}}\right)$ will have cis-trans isomers. The structures of cis-trans isomers of the alkene are shown below.

Explanation of Solution

The alkene is ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{CH}={\text{CHCH}}_{\text{2}}{\text{CH}}_{\text{3}}$.

A compound shows cis-trans isomerism when the substituents groups on the carbon atoms that are connected via double bond are different. The alkene has two different substituted groups on carbon atoms that are connected via a double bond. Therefore, it will show cis-trans isomerism. In the cis isomer, same substituted groups are on the same side of a ring or double bonds, whereas in the trans isomer same substituted groups are on a different side of a ring or double bond. Therefore, the structures of cis-trans isomers of the alkene are shown below.

Figure 1

Conclusion

The alkene $\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{CH}={\text{CHCH}}_{\text{2}}{\text{CH}}_{\text{3}}\right)$ will have cis-trans isomers. The structures of cis-trans isomers of the alkene are shown in Figure 1.

Interpretation Introduction

(c)

Interpretation:

Whether the alkene $\left({\left({\text{CH}}_{\text{3}}\right)}_2\text{C}={\text{CHCH}}_{\text{2}}{\text{CH}}_3\right)$ could exist as cis-trans isomers or not is to be predicted. The structural formulas and names of both the cis- and the trans- isomers are to be stated if the corresponding alkene shows isomerism.

Concept introduction:

Those compounds which have the same molecular formula but have different arrangements of atoms are known as isomers. The phenomenon is called isomerism. The isomers are generally classified as structural isomers and stereoisomers. Stereoisomers are further divided into two categories diastereomers and enantiomers.

Answer to Problem 12.18E

The alkene $\left({\left({\text{CH}}_{\text{3}}\right)}_2\text{C}={\text{CHCH}}_{\text{2}}{\text{CH}}_3\right)$ will not have cis-trans isomers.

Explanation of Solution

The structure of the alkene $\left({\left({\text{CH}}_{\text{3}}\right)}_2\text{C}={\text{CHCH}}_{\text{2}}{\text{CH}}_3\right)$ is shown below.

Figure 2

A compound shows cis-trans isomerism when the substituents groups on the carbon atoms that are connected via double bond are different. The alkene has the same substituted groups on a carbon atom that is on the left-hand side of the double bond. Therefore, it will not have cis-trans isomerism.

Conclusion

The alkene $\left({\left({\text{CH}}_{\text{3}}\right)}_2\text{C}={\text{CHCH}}_{\text{2}}{\text{CH}}_3\right)$ will not have cis-trans isomers.