Question

Question: a. Using Newman projections, draw all staggered and eclipsed conformations that result from rotation around the bond highlighted in pink in each molecule;

b. draw a graph of energy versus dihedral angle for rotation around this bond.

Short answer

Answer

a.

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b.

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Step-by-step solution

Rotation around the single bond in the Newman projection

The rotation around the single bond gives a different conformation.

Dihedral angle

The dihedral angle comes in the conformation when some angle separates the two sets of carbons containing three atoms.

The energy of the eclipsed conformation is the maximum (at${\mathbf{0}}^{\mathbf{0}}$ ), and that of the staggered conformation is the minimum.

Explanation

a.

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The rotation of a single bond in the Newman projection from the given molecule is obtained as:

Newman projection

$\left[2\right]$The rotation of a single bond in the given molecule is obtained as:

Newman projection

b.

The eclipsed conformation is the least stable when the two methyl groups are at$0^0$, and the maximum energy for this conformation.

The staggered conformation is the most stable and low in energy when the bulky groups are anti to each other.

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Energy versus dihedral angle graph

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Energy versus dihedral angle graph