Chapter 2, Problem 52P

(a)

Interpretation Introduction

Interpretation: The Newman projection for the rotation about the ${\text{C}}_{\text{2}}{\text{–C}}_{\text{3}}$ bond in $\text{2-methylbutane}$ should be drawn in its most stable conformation.

Concept introduction: Various interconvertible forms that result from rotation around the $\text{C–C}$ bind in ethane are termed as conformer. To depict such conformation Newman projections are written. These are obtained by conversion of hashed-wedged line structure simply when molecule is viewed in a plane along the $\text{C–C}$ as illustrated below:

  

Thus in Newman projection of simple ethane molecule the “front” $\text{C}$ is depicted as intersection of three bonds with three attached $\text{H}$ . The other three bonds connect to the large circle corresponding to “back” carbon in $\text{C–C}$ bond.

(b)

Interpretation Introduction

Interpretation: The Newman projection for the rotation about the ${\text{C}}_{\text{2}}{\text{–C}}_{\text{3}}$ bond in $\text{2,2-dimethylbutane}$ should be drawn in its most stable conformation.

Concept introduction: Various interconvertible forms that result from rotation around the $\text{C–C}$ bind in ethane are termed as conformer. To depict such conformation Newman projections are written. These are obtained by conversion of hashed-wedged line structure simply when molecule is viewed in a plane along the $\text{C–C}$ as illustrated below:

  

Thus in Newman's projection of simple ethane molecule the “front” $\text{C}$ is depicted as intersection of three bonds with three attached $\text{H}$ . The other three bonds connect to the large circle corresponding to “back” carbon in $\text{C–C}$ bond.

(c)

Interpretation Introduction

Interpretation: The Newman projection for the rotation about the ${\text{C}}_{\text{3}}{\text{–C}}_4$ bond in $\text{2,2-dimethylpentane}$ should be drawn in its most stable conformation.

Concept introduction: Various interconvertible forms that result from rotation around the $\text{C–C}$ bind in ethane are termed as conformer. To depict such conformation Newman projections are written. These are obtained by conversion of hashed-wedged line structure simply when molecule is viewed in a plane along the $\text{C–C}$ as illustrated below:

  

As rotation is carried out along ${\text{C}}_{\text{3}}{\text{–C}}_4$ axis, energy changes occur due to bond rotation from staggered to eclipsed conformation. This change amounts to torsional strain. Energy difference between eclipsed and staggered conformations corresponds to barrier that must be overcome for rotation. This is also termed as activation energy.

(d)

Interpretation Introduction

Interpretation: The Newman projection for the rotation about the ${\text{C}}_{\text{3}}{\text{–C}}_4$ bond in $\text{2,2,4-trimethylpentane}$ should be drawn in its most stable conformation.

Concept introduction: Various interconvertible forms that result from rotation around the $\text{C–C}$ bind in ethane are termed as conformer. To depict such conformation, Newman projections are written. These are obtained by conversion of hashed-wedged line structure simply when molecule is viewed in a plane along the $\text{C–C}$ as illustrated below:

  

As rotation is carried out along ${\text{C}}_{\text{3}}{\text{–C}}_4$ axis, energy changes occur due to bond rotation from staggered to eclipsed conformation. This change amounts to torsional strain. Energy difference between eclipsed and staggered conformations corresponds to barrier that must be overcome for rotation. This is also termed as activation energy.