Chapter 13, Problem 27P

Interpretation Introduction

(a)

Interpretation: The constitutional isomers formed by the monochlorination of given alkanes with ${\text{Cl}}_{\text{2}}$ and $hv$ is to be drawn.

Concept introduction: The compounds with same chemical formula but different arrangement of atoms in space are known as the constitutional isomers.

The reaction of halogen with alkane results in the formation of alkyl halide. This type of reaction is a radical substitution reaction. The halogenation of alkanes takes place via radical intermediates. If $\text{C}-\text{H}$ bond is weaker than hydrogen is replaced more readily.

Answer to Problem 27P

The five constitutional isomers formed by the reaction of $2,2,5-\text{trimethylhexane}$ with ${\text{Cl}}_{\text{2}}$ in the presence of light are,

The four constitutional isomers formed by the reaction of $1,1,3-\text{trimethylcyclobutane}$ with ${\text{Cl}}_{\text{2}}$ in the presence of light are,

Explanation of Solution

The compounds with same chemical formula but have different arrangement of atoms in space is known as the constitutional isomer.

The reaction of halogen with alkane results in the formation of alkyl halide. This type of reaction is a radical substitution reaction. The halogenation of alkanes takes place via radical intermediates. If $\text{C}-\text{H}$ bond is weaker than hydrogen is replaced more readily.

The given alkanes are shown below.

Figure 1

The given structure is in ball and stick model. The white color balls represent hydrogen atom and black color ball represents carbon atoms.

Therefore, structure of given alkanes are,

Figure 2

The constitutional isomers formed by the reaction of $2,2,5-\text{trimethylhexane}$ with ${\text{Cl}}_{\text{2}}$ in presence of light are shown below.

Figure 3

Therefore, the five constitutional isomers formed by the reaction of $2,2,5-\text{trimethylhexane}$ with ${\text{Cl}}_{\text{2}}$ in the presence of light.

Similarly, the constitutional isomers formed by the reaction of $1,1,3-\text{trimethylcyclobutane}$ with ${\text{Cl}}_{\text{2}}$ in the presence of light are shown below.

Figure 4

Therefore, the four constitutional isomers formed by the reaction of $1,1,3-\text{trimethylcyclobutane}$ with ${\text{Cl}}_{\text{2}}$ in the presence of light.

Conclusion

The constitutional isomers formed by monochlorination of given alkanes with ${\text{Cl}}_{\text{2}}$ and $hv$ is shown in Figure 3 and 4.

Interpretation Introduction

(b)

Interpretation: The major bromination product formed by heating each alkane with ${\text{Br}}_{\text{2}}$ is to be drawn.

Concept introduction: The reaction of hydrogen halide with alkane results in the formation of alkyl halide. The halogenation of alkanes takes place via radical intermediates. If $\text{C}-\text{H}$ bond is weaker than hydrogen is replaced more readily.

Answer to Problem 27P

The major product formed by the reaction of $2,2,5-\text{trimethylhexane}$ with ${\text{Br}}_{\text{2}}$ in the presence of light is,

The major product formed by the reaction of $1,1,3-\text{trimethylcyclobutane}$ with ${\text{Br}}_{\text{2}}$ in presence of light is,

Explanation of Solution

The reaction of hydrogen halide with alkane results in the formation of alkyl halide. The halogenation of alkanes takes place via radical intermediates. If $\text{C}-\text{H}$ bond is weak, then hydrogen is replaced more readily. Bromination is a selective reaction.

The major product formed by the reaction of $2,2,5-\text{trimethylhexane}$ with ${\text{Br}}_{\text{2}}$ in presence of light is shown below.

Figure 5

The major product formed by the reaction of $1,1,3-\text{trimethylcyclobutane}$ with ${\text{Br}}_{\text{2}}$ in presence of light is shown below.

Figure 6

Conclusion

The major product formed by monochlorination of given alkanes with ${\text{Br}}_{\text{2}}$ and $hv$ is shown in Figure 5 and 6.