Question

Draw the two chair conformations of each compound and label the substituents as axial and equatorial. In each case, determine which conformation is more stable.

a) Determine the stability of the conformations based on steric hindrance.
b) Determine the stability of the conformations based on electronic effects.
c) Determine the stability of the conformations based on both steric hindrance and electronic effects.
d) Determine the stability of the conformations based on the molecular weight of the compound.

Answer 1

The stability of chair conformations is determined by steric hindrance and electronic effects. Bulky groups prefer the equatorial position to minimize steric repulsion. Electron-donating groups stabilize the equatorial conformation, while electron-withdrawing groups stabilize the axial conformation. Molecular weight does not directly affect stability.

Step-by-step explanation:

When substituents are added to cyclohexane, they can be in axial or equatorial positions in the chair conformation. To determine which conformation is more stable, we consider steric hindrance and electronic effects.

a) Steric hindrance: Bulky groups experience steric repulsion when they are in axial positions. Therefore, the conformations with the bulky group in the equatorial position are more stable and predominant.

b) Electronic effects: Certain groups can donate or withdraw electron density, affecting stability. For example, electron-withdrawing groups stabilize the axial conformation, while electron-donating groups stabilize the equatorial conformation.

c) Both steric hindrance and electronic effects contribute to stability. Bulky groups in axial positions experience steric strain, while electron-donating groups stabilize the equatorial conformation.

d) Molecular weight does not directly affect the stability of chair conformations.