Which are the approximate carbon-carbon bond angles at positions I and II in the following compound? The requested sequence is I,II.

Question

Quizplus · Accepted Answer

The molecule shown is a cyclohexane ring, with each vertex representing a carbon atom. The ring adopts a chair conformation to minimize steric strain between the bulky substituents. In this conformation, the carbon atoms at positions I and II are both sp3 hybridized and have tetrahedral geometry.

The ideal bond angle for a tetrahedral geometry is 109.5°, but in cyclohexane rings, the angles are distorted due to ring strain. The geometry at position I is closer to a normal tetrahedral, so the bond angle is close to 109°. The geometry at position II is different, because the bond between the two carbons in question is part of the ring. This bond is constrained by the ring structure and cannot freely rotate, making the bond angle at position II closer to 120°.

Therefore, the approximate bond angles at positions I and II are 109° and 120°, respectively, giving us choice C as the best answer.

Which Are the Approximate Carbon-Carbon Bond Angles at Positions I