Q.73. - Organic Chemistry

Question

Question: Consider the tricyclic structure B. 

(a) Label each substituent on the rings as axial or equatorial.

(b) Draw B using chair conformations for each six-membered ring. 

(c) Label the atoms on the ring fusions (the carbons that join each set of two rings together) as cis or trans to each other.

                           B

Step-by-Step Solution

Answer

Answer

a.

b.

c. Blue-blue dots represent cis configuration, and blue-red dots represent trans configuration.

Step 1: Chair conformation of cyclohexane

The most stable conformation used to represent a cyclohexane molecule is the chair conformation.

The bonds positioned vertically on the carbon atoms of the ring (in chair conformation) are termed axial. The ones that are positioned horizontally or in a distorted manner are termed equatorial.

Step 2: Cis and trans in the chair conformation of cyclohexane

The atoms (attached to a common center) that are oriented in the same direction (either upward or downward) are said to be cis to each other.

The atoms (attached to a common center) that are oriented in the opposite direction (i.e., one points upward while the other points downward or vice-versa) are said to be trans to each other.

Step 3: Skeletal structure of B

The skeletal structure of B using the chair conformation for the six-membered rings is shown below.

Skeletal structure of B

Step 4: Axial and equatorial atoms in B

The structure of B indicating the position of the atoms as axial/equatorial is provided below.

Axial and equatorial atoms in B

Step 5: Structure of B representing the orientation of the atoms

Structures representing the configuration of fused atoms

 

In the given structure, the blue-blue dots indicate that the carbon atoms are cis to the fused carbon, while the blue-red dots indicate that the carbon atoms are trans to the fused carbon.