Which one of the following conformations of cyclohexane is the least stable ?

Options

A. Half-chair
B. Boat
C. Twisted-boat
D. Chair

Answer

A

Explanation

The half-chair can be attained by moving the carbons `C_1,C_2,C_3 and C_4` of a chair conformation into one plane and `C_6` above the plane and `C_5` below the plane. It contains many eclipsed carbon-hydrogen bonds. The half chair conformer lies about 10.8 kcal above the chair form