Question

Question: For each compound drawn below:

a. Label each OH, Br, and$\mathit{C}{\mathit{H}}_{\mathbf{3}}$group as axial or equatorial.

b. Classify each conformation as cis or trans.

c. Translate each structure into a representation with a hexagon for the six-membered ring, and wedges and dashed wedges for groups above and below the ring.

d. Draw the second possible chair conformation for each compound.

Short answer

Answer

a.

$\left[1\right]$

$\left[2\right]$

$\left[3\right]$

b.

$\left[1\right]$

$\left[2\right]$

$\left[3\right]$

c.

$\left[1\right]$

$\left[2\right]$

$\left[3\right]$

d.

$\left[1\right]$

$\left[2\right]$

$\left[3\right]$

Step-by-step solution

Chair conformation

The chair conformation is considered the most stable due to its low energy. The conformation has six (axial or equatorial) sites.

The axial and equatorial sites are represented as:

Blue represents the H-equatorial and black represents the H-axial

Cis and trans configurations in the chair conformation

The Cis conformation is determined when two sites have axial (can be up or down) substitution or equatorial substitution.

The trans conformation is obtained when two sites have one axial and one equatorial substitution.

Explanation

a. The axial group is perpendicular to the plane, and the equatorial groups are parallel to the plane.

$\left[1\right]$

Axial and equatorial (eq)

$\left[2\right]$

Axial and equatorial (eq) substituents

$\left[3\right]$

Axial and equatorial (eq) substituents

b. The cis conformation has only up or only down substitution.

The trans conformation has up and down conformations.

$\left[1\right]$

Trans chair conformation

$\left[2\right]$

Cis chair conformation

$\left[3\right]$

Trans chair conformation

c.

In the wedge dash structure of the chair conformation, the up substituent (it may be axial or equatorial) is shown above the plane, and the down substituents are shown below the plane.

$\left[1\right]$

Wedge dash structure

$\left[2\right]$

Wedge dash structure

$\left[3\right]$

Wedge dash structure

d.

When one chair conformation flips to the other, the groups are interchanged.

$\left[1\right]$

Ring flipping

$\left[2\right]$

Ring flipping

$\left[3\right]$

Ring flipping