Question

Question: Calculate the destabilization present in each eclipsed conformation.

a.

b.

Short answer

Answer

a. The destabilization energyis 3.8 kcal/mol.

b. The destabilization energy is 4.2 kcal/mol.

Step-by-step solution

Conformation

The two main types of conformations are:

• eclipsed and
• staggered.

These are based on the dihedral angle.

The conformations are shown below:

Eclipsed and Staggered

Calculation of the destabilization energy of a

a. There is one H, H and two $C{H}_3$, H eclipsing interactions in the given conformation. The value of the destabilization energyis calculated as follows:

role="math" localid="1648531767188" $$\begin{gathered} ∆E=\left[1\left(H,Heclip\sin g\right)+2\left(C{H}_3,Heclip\sin g\right)\right] \\ =\left[1\times 1.0+2\times 1.4\right]kcal/mol \\ =3.8kcal/mol \end{gathered}$$

Thus, the destabilization energy is 3.8 kcal/mol.

Calculation of the destabilization energy of b

b. There are three $C{H}_3$, H eclipsing interactions in the given conformation. The value of the destabilization energy is calculated as follows:

$$\begin{gathered} ∆E=3\left(C{H}_3,Heclip\sin g\right) \\ =\left[3\times 1.4\right]kcal/mol \\ =4.2kcal/mol \end{gathered}$$

Thus, the destabilization energy is 4.2 kcal/mol.