Chapter 2, Problem 54P

(a)

Interpretation Introduction

Interpretation: The value of free energy change between more favorable and less favorable conformations is to be calculated at $25°\text{C}$ .

Concept introduction: The formula that determines spontaneity of the reaction is,

  $\Delta G°=-RT\ln K$

Where,

• $T$denotes temperature.
• $K$denotes equilibrium constant.
• $R$denotes a gas constant.
• $\Delta G°$ denotes standard Gibbs energy.

(b)

Interpretation Introduction

Interpretation: The potential-energy diagram for rotation about the ${\text{C}}_{\text{2}}{\text{–C}}_{\text{3}}$ bond in $\text{2-methylbutane}$ and relative energy values to all the conformations should be determined.

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 the molecule is viewed in a plane along the $\text{C–C}$

as illustrated below:

(c)

Interpretation Introduction

Interpretation: All Newman projections of $\text{2-methylbutane}$ should be drawn and two most favorable ones should be indicated.

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 the 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 an 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.