Problem: Cyclohexane exists in different types of conformations. The most stable among the conformers are the chair and boat conformations. The bond angles are approximately 109.5 ° in both the chair and boat forms of cyclohexane. In the figure below (I) and (III) are the chair conformers whereas (II) is the boat conformer. The conformations keep flipping; that is, the conformations undergo interconversions, as shown in the figure below.In the conversion of the conformations of cyclohexane shown below, which of the following statements are true?Check all that apply.a) In the conversion from I to II, the dihedral angle between the hydrogen atoms on adjacent carbon atoms goes on increasing.b) In the conversion from I to III, the bond angle between the C-C-C bond of cyclohexane remains 109.5 °.c) In the conversion from I to II, steric strain is not introduced.d)  In the conversion from I to II, at Cl and C4, C-H bonds are brought closer together, increasing repulsive interactions between them.e) In the conversion from I to II, C-H bonds on C2, C3, C5, and C6 become neither axial nor equatorial.f) In the conversion from I to III, all axial bonds become equatorial, and all equatorial bonds become axial.

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FREE Expert Solution

Analyzing each statement:

a) In the conversion from I to II, the dihedral angle between the hydrogen atoms on adjacent carbon atoms goes on increasing.

False, they are decreasing


b) In the conversion from I to III, the bond angle between the C-C-C bond of cyclohexane remains 109.5 °.

True. All Cs are still sp3 hybrized following a tetrahedral geometry

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Problem Details

Cyclohexane exists in different types of conformations. The most stable among the conformers are the chair and boat conformations. The bond angles are approximately 109.5 ° in both the chair and boat forms of cyclohexane. In the figure below (I) and (III) are the chair conformers whereas (II) is the boat conformer. The conformations keep flipping; that is, the conformations undergo interconversions, as shown in the figure below.

In the conversion of the conformations of cyclohexane shown below, which of the following statements are true?

Check all that apply.

a) In the conversion from I to II, the dihedral angle between the hydrogen atoms on adjacent carbon atoms goes on increasing.

b) In the conversion from I to III, the bond angle between the C-C-C bond of cyclohexane remains 109.5 °.

c) In the conversion from I to II, steric strain is not introduced.

d)  In the conversion from I to II, at Cl and C4, C-H bonds are brought closer together, increasing repulsive interactions between them.

e) In the conversion from I to II, C-H bonds on C2, C3, C5, and C6 become neither axial nor equatorial.

f) In the conversion from I to III, all axial bonds become equatorial, and all equatorial bonds become axial.

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Chair Flip concept. You can view video lessons to learn Chair Flip. Or if you need more Chair Flip practice, you can also practice Chair Flip practice problems.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Ochoa's class at UCD.