Q.29. - Organic Chemistry

Question

Question: Draw a chair conformation of cyclohexane with one $\mathit{C}{\mathit{H}}_{\mathbf{3}}\mathit{C}{\mathit{H}}_{\mathbf{2}}$  group and one $\mathit{C}{\mathit{H}}_{\mathbf{3}}$  group that fits each description.

1. a 1,1-disubstituted cyclohexane with an axial $\mathit{C}{\mathit{H}}_{\mathbf{3}}\mathit{C}{\mathit{H}}_{\mathbf{2}}$ group
2. a cis-1,2-disubstituted cyclohexane with an axial $\mathit{C}{\mathit{H}}_{\mathbf{3}}$ group
3. a trans-1,3-disubstituted cyclohexane with an equatorial $\mathit{C}{\mathit{H}}_{\mathbf{3}}$ group
4. a trans-1,4-disubstituted cyclohexane with an equatorial $\mathit{C}{\mathit{H}}_{\mathbf{3}}\mathit{C}{\mathit{H}}_{\mathbf{2}}$ group 

Step-by-Step Solution

Answer

Answer

 

a.

b.

c.

d. 

Step 1: Conformational isomers

The stereoisomers that are easily convertible into one another by rotating about the carbon-carbon sigma bond are called conformational isomers.

These are further represented as staggered and eclipsed conformations.

Step 2: The chair conformations of cyclohexane with one ethyl and one methyl group

a. The structure of 1,1-disubstituted cyclohexane with an axial ethyl group is shown in the structure below:

1,1-disubstituted cyclohexane

 

b. The structure of cis-1,2 disubstituted cyclohexane with an axial methyl group is shown below:

Cis-1,4-disubstituted

 

 

The ethyl group in the above structure is in the equatorial position.

 

c. The trans 1,3 disubstituted cyclohexane with an equatorial methyl group is shown in the following structure:

Trans-1,3-disubstituted

 

 In the above structure, the methyl group is now present at the equatorial position, and the ethyl group is present at the axial position. 

 

d. The trans-1,4 disubstituted cyclohexane with an equatorial ethyl group is shown in the structure below:

Trans-1,4-disubstituted

 

The ethyl group, as well as the methyl group in the above structure, are present at equatorial positions.