Chapter 21, Problem 45E

If one hydrogen in a hydrocarbon is replaced by a halogen atom, the number of isomers that exist for the substituted compound depends on the number of types of hydrogen in the original hydrocarbon. Thus there is only one form of chloroethane (all hydrogens in ethane are equivalent), but there are two isomers of propane that arise from the substitution of a methyl hydrogen or a methylene hydrogen. How many isomers can be obtained when one hydrogen in each of the compounds named below is replaced by a chlorine atom?

a. n-pentane

b. 2-methylbutane

c. 2,4-dimethylpentane

d. methylcyclobutane

Interpretation Introduction

Interpretation: The number of isomers that can be obtained when one hydrogen atom in each of the given compound is replaced by a chlorine atom.

Concept introduction: Structural isomerism occurs when two compounds have same number of atoms but the spatial arrangement of the atoms is different from each other. If one hydrogen atom of a hydrocarbon is replaced by a halogen atom, the number of isomers that exists for the substituted compound depends on the number of types of hydrogen in the original hydrocarbon.

To determine: The number of isomers that can be obtained when one hydrogen in n-pentane is replaced by a chlorine atom.

Answer to Problem 45E

Answer

Three isomers are obtained when one hydrogen atom of n-pentane is replaced by a chlorine atom.

Explanation of Solution

Explanation

The isomer is $1$-chloropentane.

The given compound n-pentane has five carbon atoms in the longest carbon chain. When hydrogen of first carbon of n-pentane is replaced by chlorine atom, then the isomer named $1$-chloropentane is formed. Its structure is,

Figure 1

The isomer is $2$-chloropentane.

The given compound n-pentane has five carbon atoms in the longest carbon chain. When hydrogen of second carbon of n-pentane is replaced by chlorine atom, then the isomer named $2$-chloropentane is formed. Its structure is,

Figure 2

The parent chain contains five carbon atom and chlorine group is attached to second carbon.

The compound $2$-chloropentane is structural isomer of $1$-chloropentane because the number of atoms in both the compounds is same but their structures are different.

The isomer is $3$-chloropentane.

The given compound n-pentane have five carbon atoms in the longest carbon chain. When hydrogen of third carbon of n-pentane is replaced by chlorine atom, then the isomer named $3$-chloropentane is formed. Its structure is,

Figure 3

The compound $3$-chloropentane is structural isomer of $1$-chloropentane because the number of atoms in both the compounds is same but their structures are different.

Interpretation Introduction

Interpretation: The number of isomers that can be obtained when one hydrogen atom in each of the given compound is replaced by a chlorine atom.

Concept introduction: Structural isomerism occurs when two compounds have same number of atoms but the spatial arrangement of the atoms is different from each other. If one hydrogen atom of a hydrocarbon is replaced by a halogen atom, the number of isomers that exists for the substituted compound depends on the number of types of hydrogen in the original hydrocarbon.

To determine: The number of isomers that can be obtained when one hydrogen atom in $2$-methylbutane is replaced by a chlorine atom

Answer to Problem 45E

Answer

Nine isomers are obtained when one hydrogen of $2$-methylbutane is replaced by a chlorine atom.

Explanation of Solution

Explanation

The isomer is $1$-chloro- $2$-methylbutane.

In the given compound, $2$-methylbutane, four carbon atoms forms the parent chain. Methyl group is attached to second carbon. When hydrogen of first carbon of $2$-methylbutane is replaced by chlorine atom, then the isomer named $1$-chloro- $2$-methylbutane is formed. Its structure is,

Figure 4

The isomer is $1$-chloro- $3$-methylbutane.

In the given compound, $2$-methylbutane, four carbon atoms forms the parent chain. Methyl group is attached to second carbon. When hydrogen of first carbon of $3$-methylbutane is replaced by chlorine atom, then the isomer named $1$-chloro- $3$-methylbutane is formed. Its structure is,

Figure 5

The isomer is $2$-chloro- $3$-methylbutane.

In the given compound, $2$-methylbutane, four carbon atoms forms the parent chain. Methyl group is attached to second carbon. When hydrogen of second carbon of $3$-methylbutane is replaced by chlorine atom, then the isomer named $2$-chloro- $3$-methylbutane is formed. Its structure is,

Figure 6

The isomer is $2$-chloro- $2$-methylbutane.

In the given compound, $2$-methylbutane, four carbon atoms forms the parent chain. Methyl group is attached to second carbon. When hydrogen of second carbon of $2$-methylbutane is replaced by chlorine atom, then the isomer named $2$-chloro- $2$-methylbutane is formed. Its structure is,

Figure 7

The isomer is $1$-chloro- $2,2$-dimethylpropane.

In the given compound, $2$-methylbutane, four carbon atoms forms the parent chain. Methyl group is attached to second carbon. When hydrogen of second carbon of $2$-methylbutane is replaced by chlorine atom, then the isomer named $2$-chloro- $2$-methylbutane is formed. Its structure is,

Figure 8

The isomer is $1$-chloro- $2$-methylbutane.

In the given compound, $2$-methylbutane, four carbon atoms forms the parent chain. Methyl group is attached to second carbon. When hydrogen of first carbon of $2$-methylbutane is replaced by chlorine atom, then the isomer named $1$-chloro- $2$-methylbutane is formed. Its structure is,

Figure 9

The isomer is $2$-chloro- $2$-methylbutane.

In the given compound, $2$-methylbutane, four carbon atoms forms the parent chain. Methyl group is attached to second carbon. When hydrogen of second carbon of $2$-methylbutane is replaced by chlorine atom, then the isomer named $2$-chloro- $2$-methylbutane is formed. Its structure is,

Figure 10

The isomer is $2$-chloro- $3$-methylbutane.

In the given compound, $2$-methylbutane, four carbon atoms forms the parent chain. Methyl group is attached to second carbon. When hydrogen of third carbon of $2$-methylbutane is replaced by chlorine atom, then the isomer named $2$-chloro- $3$-methylbutane is formed. Its structure is,

Figure 11

The isomer is $1$-chloro- $3$-methylbutane.

In the given compound, $2$-methylbutane, four carbon atoms forms the parent chain. Methyl group is attached to second carbon. When hydrogen of fourth carbon of $2$-methylbutane is replaced by chlorine atom, then the isomer named $1$-chloro- $3$-methylbutane is formed. Its structure is,

Figure 12

Interpretation Introduction

Interpretation: The number of isomers that can be obtained when one hydrogen atom in each of the given compound is replaced by a chlorine atom.

Concept introduction: Structural isomerism occurs when two compounds have same number of atoms but the spatial arrangement of the atoms is different from each other. If one hydrogen atom of a hydrocarbon is replaced by a halogen atom, the number of isomers that exists for the substituted compound depends on the number of types of hydrogen in the original hydrocarbon.

To determine: The number of isomers that can be obtained when one hydrogen in $2,4$-dimethylpentane is replaced by a chlorine atom.

Answer to Problem 45E

Answer

Two isomers are obtained when one hydrogen of $2,4$-dimethylpentane is replaced by a chlorine atom.

Explanation of Solution

Explanation

The isomer is $2$-chloro- $2,4$-dimethylpentane.

The given compound $2,4$-dimethylpentane have five carbons in the parent chain. Two methyl groups are attached at second and fourth carbon. When hydrogen of second carbon of the parent chain is replaced by chlorine atom, then the isomer named $2$-chloro- $2,4$-dimethylpentane is formed. Its structure is,

Figure 13

The isomer is $3$-chloro- $2,4$-dimethylpentane.

The given compound $2,4$-dimethylpentane have five carbons in the parent chain. Two methyl groups are attached at second and fourth carbon. When hydrogen of third carbon of the parent chain is replaced by chlorine atom, then the isomer named $3$-chloro- $2,4$-dimethylpentane is formed. Its structure is,

Figure 14

Interpretation Introduction

Interpretation: The number of isomers that can be obtained when one hydrogen atom in each of the given compound is replaced by a chlorine atom.

Concept introduction: Structural isomerism occurs when two compounds have same number of atoms but the spatial arrangement of the atoms is different from each other. If one hydrogen atom of a hydrocarbon is replaced by a halogen atom, the number of isomers that exists for the substituted compound depends on the number of types of hydrogen in the original hydrocarbon.

To determine: The number of isomers that can be obtained when one hydrogen in methylcyclobutane is replaced by a chlorine atom.

Answer to Problem 45E

Answer

Three isomers are obtained when one hydrogen of methylcyclobutane is replaced by a chlorine atom.

Explanation of Solution

Explanation

The isomer is $1$-chloromethylcyclobutane.

In the given compound methylcyclobutane, the ring of four carbon atoms is considered as the parent chain. Methyl group is attached at first carbon. When hydrogen of the methyl group is replaced by chlorine atom, then the isomer named $1$-chloromethylcyclobutane is formed. Its structure is,

Figure 15

The isomer is $1$-chloro- $2$-methylcyclobutane.

In the given compound methylcyclobutane, the ring of four carbon atoms is considered as the parent chain. Methyl group is attached at first carbon. When hydrogen of the second carbon of the ring is replaced by chlorine atom, then the isomer named $1$-chloro- $2$-methylcyclobutane is formed. Its structure is,

Figure 16

The isomer is $1$-chloro- $3$-methylcyclobutane.

In the given compound methylcyclobutane, the ring of four carbon atoms is considered as the parent chain. Methyl group is attached at first carbon. When hydrogen of the third carbon of the ring is replaced by chlorine atom, then the isomer named $1$-chloro- $3$-methylcyclobutane is formed. Its structure is,

Figure 17