The Most Stable Conformation Of Cis-1-Tert-Butyl-2-Mothylcyclohexane Is The One In Which:
A) The Tert -Butyl Group Is Axial And The Methyl Group In Equatorial.
B) The Methyl Group Is Axial And The Tert -Butyl Group Is Equatorial.
C) Both Groups Are Axial.
D) Both Groups Are Equatorial.
E) None Of The Above
The correct answer and explanation is :
The correct answer is B) The Methyl Group Is Axial And The Tert-Butyl Group Is Equatorial.
Explanation:
To determine the most stable conformation of cis-1-tert-butyl-2-methylcyclohexane, we need to consider the following factors:
- Steric Hindrance and Size of Groups:
- Tert-butyl group (C₄H₉) is bulky and will experience significant steric strain if placed in the axial position. This is because axial positions in cyclohexane conformations are in close proximity to the other axial substituents on the same side of the ring (called 1,3-diaxial interactions). These interactions cause steric hindrance and lead to increased strain when a large group occupies the axial position.
- Methyl group (CH₃) is smaller and can more easily be accommodated in the axial position because it doesn’t introduce as much steric strain compared to the tert-butyl group.
- Conformation of Cyclohexane Rings:
- The chair conformation of cyclohexane allows for substituents to occupy either axial or equatorial positions.
- The equatorial position is generally more favorable for large substituents, such as the tert-butyl group, because it minimizes steric interactions.
- The axial position is typically preferred for smaller substituents, like the methyl group, to avoid steric clashes.
Most Stable Conformation:
In the cis form of 1-tert-butyl-2-methylcyclohexane:
- The tert-butyl group will prefer to be equatorial because it is large and its axial positioning would create significant steric hindrance (1,3-diaxial interactions).
- The methyl group will prefer to be axial since it is smaller and can fit better in this position with less steric interference.
Thus, the most stable conformation is one where the tert-butyl group is equatorial, and the methyl group is axial.
Image:
Here’s a diagram of the two possible chair conformations of cis-1-tert-butyl-2-methylcyclohexane, showing the most stable conformation (with tert-butyl equatorial and methyl axial).
