Question

Question: Consider rotation around the carbon-carbon bond in 1,2-dichloroethane $\left(ClC{H}_{2}C{H}_{2}Cl\right)$.

a.Using Newman projections, draw all of the staggered and eclipsed conformations that result from rotation around this bond.

b. Graph energy versus dihedral angle for rotation around this bond.

Short answer

Answer

a.

b.

Step-by-step solution

Step 1:Stability and energy

The energy of the conformation is based upon the repulsion of the bulky groups. The more the repulsion, the more will be energy.

Also, the conformation will be unstable.

Newman projection

The given compound is 1,2-dichloroethane. The Newman projection for the given compound is shown below:

Newman projection for 1,2-dichloroethane

Explanation

a.

By fixing the front carbon, the back carbon is rotated by ${60}^0$. As a result, three staggered and three eclipsed conformations are produced as shown below:

Conformation of 1,2-dichloroethane

b.

The relation between the positions of the bulky groups with energy and stability is mentioned below:

• When the two bulkier groups (chlorine) are anti or opposite to each other, the energy of the conformation is the minimum, and it is stable.
• When the two bulkier groups (chlorine) are at ${120}^0$, the energy of the conformation is larger as above, and it is slightly stable.
• When the two bulkier groups (chlorine) are at ${60}^0$, the energy of the conformation is the largest as the above two conformations, and it is unstable.

The graph between energy and dihedral angle is shown below:

Graph representing energy and dihedral angle