Question

consider the following compound.(a)assign r or s configuration to each marked chiral center of two different atropisomers that could be isolated at lower temperature.a: b: c: d: (b)will the compound show any optical activity if there is restricted rotation along the central bond?atropisomers are stereoisomers that occur when rotation restriction around a central bond is to allow isolation of individual conformers. the two atropisomers shown in (a) a plane of symmetry, so pure samples of each rotate the plane of plane polarized light.(c)what will happen to the optical activity at elevated temperatures as the rotation becomes less restricted?at higher temperature, as rotation becomes less restricted, the molecule becomes a meso compound because the chiral centers marked a and b have substituents on them and possess and chirality, respectively. therefore, as rotation of the central bond becomes less restricted, the optical rotation of either isolated conformer will be until it reaches a when full rotation is observed.submit answertry another version3 item attempts remaining

Answer 1

For the following:

• (a) The two conformers of an atropisomer can be considered distinct molecules due to restricted rotation.
• (b) The two conformers each have a chiral center, so each conformer can rotate the plane of polarized light in a specific direction.
• (c) The optical activity of the compound decreases with increasing temperature and eventually reaches zero at high temperatures.

What occurs in this compound?

a) Atropisomers are stereoisomers that arise from restricted rotation around a single bond. Due to this restricted rotation, the two conformers of an atropisomer cannot interconvert freely, and each conformer can be considered a distinct molecule. In this case, there are two chiral centers in the molecule, labeled A and B. The assignment of R or S configuration to each chiral center depends on the orientation of the substituents around the chiral center.

Atropisomer 1:

Chiral center A: S configuration

Chiral center B: R configuration

Atropisomer 2:

Chiral center A: R configuration

Chiral center B: S configuration

b) The compound will show optical activity if there is restricted rotation along the central bond. This is because the two conformers of the atropisomer are no longer able to interconvert freely, so they effectively act as separate molecules. Each conformer has a chiral center, so each conformer can rotate the plane of polarized light in a specific direction.

c) As the temperature increases, the rotation around the central bond becomes less restricted, and the two conformers of the atropisomer are able to interconvert more freely. At high temperatures, the interconversion becomes so rapid that the two conformers cannot be distinguished, and the molecule becomes a meso compound.

In this case, the plane of symmetry passes through the central bond and the two chiral centers. As a result, the optical activity of the compound decreases with increasing temperature and eventually reaches zero at high temperatures.