Chapter 25, Problem 25.32P

Interpretation Introduction

(a)

Interpretation:

The weakest $\text{C-H}$ bond in the given compound is to be determined.

Concept introduction:

The carbon atom attached to more number of alkyl group form weaker bond $\text{(i}\text{.e}{\text{. 1}}^{\text{o}}{\text{ >2}}^{\text{o}}{\text{ > 3}}^{\text{o}}\text{)}$ because the resulting ${\text{C}}^{\text{•}}$ is stabilized by addition electron-donating alkyl group. Also bonds involving allylic or benzylic C atoms tend to be weaker because of the resonance stabilization in the resulting alkyl radical. When C is the part of a $\text{C=C}$ bond (i.e, vinylic or aromatic) owing to additional s characters tends to form a strong bond.

The weakest bond has the smallest bond dissociation energy value.

Answer to Problem 25.32P

The weakest $\text{C-H}$ bond in the given compound is marked:

Explanation of Solution

The given compound with types of $\text{C-H}$ bond is:

Here different types of $\text{C-H}$ bonds are present in the compound; primary, secondary, vinylic, secondary allylic and tertiary allylic. The $\text{C-H}$ bonds involving C is weaker when the C has more alkyl group. Thus tertiary $\text{C-H}$ bond is weaker bond in addition to that it is tertiary allylic bond however, therefore, it become weakest because the resonance stabilization in the resulting alkyl radical.

The weakest bond in the given compound is marked in the square:

Conclusion

The weakest $\text{C-H}$ bond in the given compound is indentified on the basis of the type of $\text{C-H}$ bonds present in the compound.

Interpretation Introduction

(b)

Interpretation:

The weakest $\text{C-H}$ bond in the given compound is to be determined.

Concept introduction:

The carbon atom attached to more number of alkyl group form weaker bond $\text{(i}\text{.e}{\text{. 1}}^{\text{o}}{\text{ >2}}^{\text{o}}{\text{ > 3}}^{\text{o}}\text{)}$ because the resulting ${\text{C}}^{\text{•}}$ is stabilized by addition electron-donating alkyl group. Also bonds involving allylic or benzylic C atoms tend to be weaker because of the resonance stabilization in the resulting alkyl radical. When C is the part of a $\text{C=C}$ bond (i.e, vinylic or aromatic) owing to additional s characters tends to form a strong bond.

The weakest bond has the smallest bond dissociation energy value.

Answer to Problem 25.32P

The weakest $\text{C-H}$ bond in the given compound is marked:

Explanation of Solution

The given compound with types of $\text{C-H}$ bond is:

Here different types of $\text{C-H}$ bonds are present in the compound; primary, secondary, tertiary, aromatic and tertiary benzylic. The $\text{C-H}$ bonds involving C is weaker when the C has more alkyl group. Thus tertiary $\text{C-H}$ bond is weaker bond in addition to that it is tertiary benzylic bond however, therefore, it become weakest because the resonance stabilization in the resulting benzylic radical.

The weakest bond in the given compound is marked in the square:

Conclusion

The weakest $\text{C-H}$ bond in the given compound is indentified on the basis of the type of $\text{C-H}$ bonds present in the compound.

Interpretation Introduction

(c)

Interpretation:

The weakest $\text{C-H}$ bond in the given compound is to be determined.

Concept introduction:

The carbon atom attached to more number of alkyl group form weaker bond $\text{(i}\text{.e}{\text{. 1}}^{\text{o}}{\text{ >2}}^{\text{o}}{\text{ > 3}}^{\text{o}}\text{)}$ because the resulting ${\text{C}}^{\text{•}}$ is stabilized by addition electron-donating alkyl group. Also bonds involving allylic or benzylic C atoms tend to be weaker because of the resonance stabilization in the resulting alkyl radical. When C is the part of a $\text{C=C}$ bond (i.e, vinylic or aromatic) owing to additional s characters tends to form a strong bond.

The weakest bond has the smallest bond dissociation energy value.

Answer to Problem 25.32P

The weakest $\text{C-H}$ bond in the given compound is marked:

Explanation of Solution

The given compound with types of $\text{C-H}$ bond is:

Here different types of $\text{C-H}$ bonds are present in the compound; primary, secondary. The $\text{C-H}$ bonds involving C is weaker when the C has more alkyl group. Thus secondary $\text{C-H}$ bond is weaker bond. There are two secondary $\text{C-H}$ bonds but the primary $\text{C-H}$ bond adjacent to the $\text{COH}$ is the weakest bond as it undergo homolysis to produce an alkyl radical that is resonance stabilized.

The weakest bond in the given compound is marked in the square:

Conclusion

The weakest $\text{C-H}$ bond in the given compound is indentified on the basis of the type of $\text{C-H}$ bonds present in the compound.