Which of the following is the most stable conformation of $\mathrm{Br}$omocyclohexane?

• A. Boat conformation with the $\mathrm{Br}$omine atom in the equatorial position
• B. Boat conformation with the $\mathrm{Br}$omine atom in the axial position
• C. Chair conformation with the $\mathrm{Br}$omine atom in the axial position
• D. Chair conformation with the $\mathrm{Br}$omine atom in the equatorial position

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the conformations of cyclohexane. Cyclohexane primarily adopts two conformations: chair and boat. The chair conformation is generally more stable due to minimized torsional strain and steric hindrance, while the boat conformation is less stable because of increased steric strain and flagpole interactions.
2. Step 2: Identify the positions on the cyclohexane ring where substituents can be located: axial (perpendicular to the ring plane) and equatorial (roughly in the plane of the ring). Substituents in the equatorial position experience less steric hindrance compared to those in the axial position.
3. Step 3: Consider the size and steric bulk of the substituent, in this case, bromine (Br). Bromine is a relatively large atom, so it prefers the equatorial position to minimize 1,3-diaxial interactions that occur when bulky groups are axial.
4. Step 4: Compare the stability of the four given options by combining the conformation and substituent position: chair vs. boat and axial vs. equatorial. The chair conformation with the bromine in the equatorial position minimizes both ring strain and steric hindrance, making it the most stable.
5. Step 5: Conclude that the most stable conformation of bromocyclohexane is the chair conformation with the bromine substituent in the equatorial position, as this arrangement reduces steric strain and torsional strain effectively.