Question

The molecule that gets inter-converted into its enantiomer, upon ring flipping in its chair conformation, is _ _ _.

• A. cis-1,2-dimethylcyclohexane
• B. cis-1,3-dimethylcyclohexane
• C. cis-1,4-dimethylcyclohexane
• D. trans-1,2-dimethylcyclohexane

Hint:

Only those cyclohexane derivatives form enantiomers on ring flip which lose symmetry and become chiral after axial–equatorial interchange

Answer 1

The Correct Option is A

Step 1: What a chair flip changes.
A chair flip turns every axial group equatorial and every equatorial group axial. It does not change whether two groups are cis or trans.

Step 2: When the flip gives the enantiomer.
The flipped chair is the mirror image only when the molecule has no plane of symmetry. If a symmetry plane is present, the flip just gives back the same molecule.

Step 3: Test the choices.
cis-1,3 and cis-1,4 forms keep a plane of symmetry, and the trans-1,2 form also stays the same on flipping. Only cis-1,2-dimethylcyclohexane has no such plane.

Step 4: Answer.
\[ \boxed{\text{cis-1,2-dimethylcyclohexane}} \]