Chapter 22, Problem 2Q

(a)

Interpretation Introduction

Interpretation:

The type of isomerism that could be exhibited by the given formulae and an example that illustrates the specific type of isomerism has to be stated.

Concept introduction:

Organic compounds which have similar chemical formula but different structures, i.e., the atoms are in a different spatial arrangement, they are known as structural isomers. Cis and Trans isomers are also structural or geometrical isomers.

Answer to Problem 2Q

${\text{C}}_{\text{6}}{\text{H}}_{12}$ exhibits both structural and geometrical isomerism.

Explanation of Solution

The type of isomerism that could be exhibited by ${\text{C}}_{\text{6}}{\text{H}}_{12}$ and an example that illustrates the specific type of isomerism.

The structural isomer of ${\text{C}}_{\text{6}}{\text{H}}_{12}$ is $1$-hexene.

The given formula, ${\text{C}}_{\text{6}}{\text{H}}_{12}$ has six carbon atoms and twelve hydrogen atoms. $1$-hexene also has six carbon atoms and twelve hydrogen atoms but their structures are different. Therefore, $1$-hexene is a structural isomer of ${\text{C}}_{\text{6}}{\text{H}}_{12}$.

The root word hexene indicates that six carbon atoms are present in the parent chain. Double bond is present between first and second carbon.

The structure of 1-hexene is shown

The structural isomer of ${\text{C}}_{\text{6}}{\text{H}}_{12}$ is $2$-hexene.

The given formula, ${\text{C}}_{\text{6}}{\text{H}}_{12}$ has six carbon atoms and twelve hydrogen atoms. $2$-hexene also has six carbon atoms and twelve hydrogen atoms but their structures are different. Therefore, $2$-hexene is a structural isomer of ${\text{C}}_{\text{6}}{\text{H}}_{12}$.

The root word hexene indicates that six carbon atoms are present in the parent chain. The number $2$ indicates that the double bond is present between second and third carbon.

The structure of 2-hexene is shown

The structural isomer of ${\text{C}}_{\text{6}}{\text{H}}_{12}$ is $3$-hexene.

The given formula, ${\text{C}}_{\text{6}}{\text{H}}_{12}$ has six carbon atoms and twelve hydrogen atoms. $3$-hexene also has six carbon atoms and twelve hydrogen atoms but their structures are different. Therefore, $3$-hexene is a structural isomer of ${\text{C}}_{\text{6}}{\text{H}}_{12}$.

The root word hexene indicates that six carbon atoms are present in the parent chain. The number $3$ indicates that the double bond is present between the third and fourth carbon.

The structure of 3-hexene is shown

The structural isomer of ${\text{C}}_{\text{6}}{\text{H}}_{12}$ is $3$-methylpent- $2$-ene.

The given formula, ${\text{C}}_{\text{6}}{\text{H}}_{12}$ has six carbon atoms and twelve hydrogen atoms. $3$-methylpent- $2$-ene also has six carbon atoms and twelve hydrogen atoms but their structures are different. Therefore, $3$-methylpent- $2$-ene is a structural isomer of ${\text{C}}_{\text{6}}{\text{H}}_{12}$.

The root word pentene indicates that five carbon atoms are present in the parent chain. The number $2$ indicates that the double bond is present between second and third carbon. The number $3$ indicates that the methyl group is attached to the third carbon.

The structure of $3$-methylpent-2-ene is shown,

The structural isomer of ${\text{C}}_{\text{6}}{\text{H}}_{12}$ is $2,3$-dimethylbut- $2$-ene.

The given formula, ${\text{C}}_{\text{6}}{\text{H}}_{12}$ has six carbon atoms and twelve  hydrogen atoms. $2,3$-dimethylbut- $2$-ene also has six carbon atoms and twelve hydrogen atoms but their structures are different. Therefore, $2,3$-dimethylbut- $2$-ene is a structural isomer of ${\text{C}}_{\text{6}}{\text{H}}_{12}$

The root word butene indicates that six carbon atoms are present in the parent chain. The double bond is present between second and third carbon. Two methyl groups are attached at second and third carbon.

The structure of $2,3$-dimethylbut-2-ene is shown,

The geometric isomer of ${\text{C}}_{\text{6}}{\text{H}}_{12}$ is cis- $2$-hexene and trans- $2$-hexene.

The structure of cis-2-hexene is,

The structure of trans-2-hexene is,

In the cis isomer, the two hydrogen of the double bonded carbons are adjacent to each other while in trans isomer, they are opposite to each other.

The geometric isomer of ${\text{C}}_{\text{6}}{\text{H}}_{12}$ is cis- $3$-hexene and trans- $3$-hexene.

The structure of cis-3-hexene is,

The structure of trans-3-hexene is,

In the cis isomer, the two hydrogen of the double bonded carbons are adjacent to each other while in trans isomer, they are opposite to each other.

(b)

Interpretation Introduction

Interpretation:

The type of isomerism that could be exhibited by the given formulae and an example that illustrates the specific type of isomerism has to be stated.

Concept introduction:

Organic compounds which have similar chemical formula but different structures, i.e., the atoms are in a different spatial arrangement, they are known as structural isomers. Cis and Trans isomers are also structural or geometrical isomers.

Answer to Problem 2Q

${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$ exhibits both structural and optical isomerism.

Explanation of Solution

The type of isomerism that could be exhibited by ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$ and an example that illustrates the specific type of isomerism.

The structural isomer of ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$ is pentan-1-ol.

${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$ have five carbon atoms, ten hydrogen atoms and one oxygen atom. pentan-1-ol also have five carbon atoms, ten hydrogen atoms and one oxygen atom  but their structures are different. Therefore, pentan-1-ol is a structural isomer of ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$.

The root word pentane indicates that five carbon atoms are present in the parent chain. Hydroxyl group is attached to first carbon.

The structure of pentan-1-ol is shown,

The structural isomer of ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$ is 1-methoxybutane.

${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$ have five carbon atoms, ten hydrogen atoms and one oxygen atom. $1$-methoxybutane also have five carbon atoms, ten hydrogen atoms and one oxygen atom  but their structures are different. Therefore, $1$-methoxybutane is a structural isomer of ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$.

The root word butane indicates that four carbon atoms are present in the parent chain. $1$-methoxy indicates that ether group is present and methyl group is attached to the oxygen of ether group.

The structure of $1$-methoxybutane is shown,

The structural isomer of ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$ is 2-ethoxypropane.

${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$ have five carbon atoms, ten hydrogen atoms and one oxygen atom. $2$-ethoxypropane also have five carbon atoms, ten hydrogen atoms and one oxygen atom  but their structures are different. Therefore, $2$-ethoxypropane is a structural isomer of ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$.

The root word propane indicates that three carbon atoms are present in the parent chain. $2$-ethoxy indicates that ether group is present and ethyl group is attached to the oxygen of ether group and second carbon of propane chain is attached to oxygen.

The structure of 2-ethoxypropane is shown

The structural isomer of ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$ is 2-methoxybutane.

${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$ have five carbon atoms, ten hydrogen atoms and one oxygen atom. v also have five carbon atoms, ten hydrogen atoms and one oxygen atom but their structures are different. Therefore, $2$-methoxybutane is a structural isomer of ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$.

The root word butane indicates that four carbon atoms are present in the parent chain. $2$-methoxy indicates that ether group is present and methyl group is attached to the oxygen of ether group and second carbon of butane chain is attached to oxygen.

The structure of 2-methoxybutane is shown

The structural isomer of ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$ is pentan-3-ol.

${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$ have five carbon atoms, ten hydrogen atoms and one oxygen atom. pentan- $3$-ol also have five carbon atoms, ten hydrogen atoms and one oxygen atom but their structures are different. Therefore, pentan- $3$-ol is a structural isomer of ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$.

The root word pentane indicates that five carbon atoms are present in the parent chain. Hydroxyl group is attached to third carbon.

The structure of pentan- $3$-ol is shown,

The structural isomer of ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$ is pentan-2-ol.

${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$ have five carbon atoms, ten hydrogen atoms and one oxygen atom. pentan- $2$-ol also have five carbon atoms, ten hydrogen atoms and one oxygen atom but their structures are different. Therefore, pentan- $2$-ol is a structural isomer of ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}$.

The root word pentane indicates that five carbon atoms are present in the parent chain. Hydroxyl group is attached to second carbon.

The structure of pentan- $2$-ol is shown,

(c)

Interpretation Introduction

Interpretation:

The type of isomerism that could be exhibited by the given formulae and an example that illustrates the specific type of isomerism has to be stated.

Concept introduction:

Organic compounds which have similar chemical formula but different structures, i.e., the atoms are in a different spatial arrangement, they are known as structural isomers. Cis and Trans isomers are also structural or geometrical isomers.

Answer to Problem 2Q

${\text{C}}_{\text{6}}{\text{H}}_{\text{4}}{\text{Br}}_{\text{2}}$ exhibits only structural isomerism.

Explanation of Solution

The type of isomerism that could be exhibited by ${\text{C}}_{\text{6}}{\text{H}}_{\text{4}}{\text{Br}}_{\text{2}}$ and an example that illustrates the specific type of isomerism.

The structural isomer of ${\text{C}}_{\text{6}}{\text{H}}_{\text{4}}{\text{Br}}_{\text{2}}$ is $1,2$-dibromobenzene.

In ${\text{C}}_{\text{6}}{\text{H}}_{\text{4}}{\text{Br}}_{\text{2}}$, six carbon atoms, four hydrogen atoms and two bromine atoms are present. $1,2$-dibromobenzene also have six carbon atoms, four hydrogen atoms and two bromine atoms. In $1,2$-dibromobenzene, two bromine atoms are attached to benzene ring at first and second position, therefore prefix di is used. Its structure is,

The structural isomer of ${\text{C}}_{\text{6}}{\text{H}}_{\text{4}}{\text{Br}}_{\text{2}}$ is $1,3$-dibromobenzene.

In ${\text{C}}_{\text{6}}{\text{H}}_{\text{4}}{\text{Br}}_{\text{2}}$, six carbon atoms, four hydrogen atoms and two bromine atoms are present. $1,3$-dibromobenzene also have six carbon atoms, four hydrogen atoms and two bromine atoms. In $1,3$-dibromobenzene, two bromine atoms are attached to benzene ring at first and third position, therefore prefix di is used. Its structure is,

The structural isomer of ${\text{C}}_{\text{6}}{\text{H}}_{\text{4}}{\text{Br}}_{\text{2}}$ is $1,4$-dibromobenzene.

In ${\text{C}}_{\text{6}}{\text{H}}_{\text{4}}{\text{Br}}_{\text{2}}$, six carbon atoms, four hydrogen atoms and two bromine atoms are present. $1,4$-dibromobenzene also have six carbon atoms, four hydrogen atoms and two bromine atoms. In $1,4$-dibromobenzene, two bromine atoms are attached to benzene ring at first and third position, therefore prefix di is used. Its structure is,